{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-115693",
        "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "state": "PUBLISHED",
        "assignerShortName": "EEF",
        "dateReserved": "2026-10-25T10:45:02.327Z",
        "datePublished": "2026-10-26T13:49:29.374Z",
        "dateUpdated": "2026-10-26T13:49:29.374Z"
    },
    "containers": {
        "cna": {
            "affected": [
                {
                    "collectionURL": "https://repo.hex.pm",
                    "cpes": [
                        "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "hackney_ssl"
                    ],
                    "packageName": "hackney",
                    "packageURL": "pkg:hex/hackney",
                    "product": "hackney",
                    "programFiles": [
                        "src/hackney_ssl.erl"
                    ],
                    "programRoutines": [
                        {
                            "name": "hackney_ssl:ssl_opts/2"
                        },
                        {
                            "name": "hackney_ssl:merge_ssl_opts/3"
                        },
                        {
                            "name": "hackney_ssl:partial_chain/1"
                        }
                    ],
                    "repo": "https://github.com/benoitc/hackney",
                    "vendor": "benoitc",
                    "versions": [
                        {
                            "lessThan": "4.9.0",
                            "status": "affected",
                            "version": "1.24.0",
                            "versionType": "semver"
                        }
                    ]
                },
                {
                    "collectionURL": "https://github.com",
                    "cpes": [
                        "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "hackney_ssl"
                    ],
                    "packageName": "benoitc/hackney",
                    "packageURL": "pkg:github/benoitc/hackney",
                    "product": "hackney",
                    "programFiles": [
                        "src/hackney_ssl.erl"
                    ],
                    "programRoutines": [
                        {
                            "name": "hackney_ssl:ssl_opts/2"
                        },
                        {
                            "name": "hackney_ssl:merge_ssl_opts/3"
                        },
                        {
                            "name": "hackney_ssl:partial_chain/1"
                        }
                    ],
                    "repo": "https://github.com/benoitc/hackney",
                    "vendor": "benoitc",
                    "versions": [
                        {
                            "lessThan": "915eb5737e9c489d8fc22eec8cdae30e9b027be4",
                            "status": "affected",
                            "version": "d8a9afcf5c3849904274e2eba1df56c63d1a1a0c",
                            "versionType": "git"
                        }
                    ]
                }
            ],
            "configurations": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>The caller passes <code>cacerts</code> or <code>cacertfile</code> in <code>ssl_options</code> to restrict trust to a private CA, without a <code>partial_chain</code> of its own. Connections that use hackney's default certifi trust store are not affected.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "The caller passes `cacerts` or `cacertfile` in `ssl_options` to restrict trust to a private CA, without a `partial_chain` of its own. Connections that use hackney's default certifi trust store are not affected."
                        }
                    ],
                    "value": "The caller passes cacerts or cacertfile in ssl_options to restrict trust to a private CA, without a partial_chain of its own. Connections that use hackney's default certifi trust store are not affected."
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "cpeMatch": [
                                {
                                    "criteria": "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*",
                                    "versionEndExcluding": "4.9.0",
                                    "versionStartIncluding": "1.24.0",
                                    "vulnerable": true
                                }
                            ],
                            "negate": false,
                            "operator": "OR"
                        }
                    ],
                    "operator": "AND"
                }
            ],
            "credits": [
                {
                    "lang": "en",
                    "type": "finder",
                    "value": "Martin Karrer"
                },
                {
                    "lang": "en",
                    "type": "remediation developer",
                    "value": "Martin Karrer"
                },
                {
                    "lang": "en",
                    "type": "coordinator",
                    "value": "Jonatan Männchen / EEF"
                }
            ],
            "dateAssigned": "2026-10-26T09:57:53.000Z",
            "datePublic": "2026-10-25T00:00:00.000Z",
            "descriptions": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>Improper Certificate Validation vulnerability in <code>hackney_ssl</code> in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. hackney adds <code>{partial_chain, fun hackney_ssl:partial_chain/1}</code> to every <code>verify_peer</code> configuration. The callback returns any certificate in the peer chain whose public key matches a root in the bundled certifi store as the trust anchor, and OTP honours that callback over the configured <code>cacerts</code>. <code>hackney_ssl:merge_ssl_opts/3</code> kept the callback when the caller replaced the trust store with <code>cacerts</code> or <code>cacertfile</code> in <code>ssl_options</code>, so a connection pinned to a private CA still accepted any chain that carried a publicly trusted root.</p>\n<p>The hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname.</p>\n<p>This issue affects hackney: from 1.24.0 before 4.9.0.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "Improper Certificate Validation vulnerability in `hackney_ssl` in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. hackney adds `{partial_chain, fun hackney_ssl:partial_chain/1}` to every `verify_peer` configuration. The callback returns any certificate in the peer chain whose public key matches a root in the bundled certifi store as the trust anchor, and OTP honours that callback over the configured `cacerts`. `hackney_ssl:merge_ssl_opts/3` kept the callback when the caller replaced the trust store with `cacerts` or `cacertfile` in `ssl_options`, so a connection pinned to a private CA still accepted any chain that carried a publicly trusted root.\n\nThe hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname.\n\nThis issue affects hackney: from 1.24.0 before 4.9.0."
                        }
                    ],
                    "value": "Improper Certificate Validation vulnerability in hackney_ssl in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. hackney adds {partial_chain, fun hackney_ssl:partial_chain/1} to every verify_peer configuration. The callback returns any certificate in the peer chain whose public key matches a root in the bundled certifi store as the trust anchor, and OTP honours that callback over the configured cacerts. hackney_ssl:merge_ssl_opts/3 kept the callback when the caller replaced the trust store with cacerts or cacertfile in ssl_options, so a connection pinned to a private CA still accepted any chain that carried a publicly trusted root.\n\nThe hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname.\n\nThis issue affects hackney: from 1.24.0 before 4.9.0."
                }
            ],
            "impacts": [
                {
                    "capecId": "CAPEC-94",
                    "descriptions": [
                        {
                            "lang": "en",
                            "supportingMedia": [
                                {
                                    "base64": false,
                                    "type": "text/html",
                                    "value": "<p>An attacker positioned between the client and a server pinned to a private CA, holding a publicly trusted certificate for the pinned hostname, can impersonate the server and read or modify the traffic the client sends and receives.</p>"
                                },
                                {
                                    "base64": false,
                                    "type": "text/markdown",
                                    "value": "An attacker positioned between the client and a server pinned to a private CA, holding a publicly trusted certificate for the pinned hostname, can impersonate the server and read or modify the traffic the client sends and receives."
                                }
                            ],
                            "value": "An attacker positioned between the client and a server pinned to a private CA, holding a publicly trusted certificate for the pinned hostname, can impersonate the server and read or modify the traffic the client sends and receives."
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV4_0": {
                        "Automatable": "NOT_DEFINED",
                        "Recovery": "NOT_DEFINED",
                        "Safety": "NOT_DEFINED",
                        "attackComplexity": "HIGH",
                        "attackRequirements": "PRESENT",
                        "attackVector": "NETWORK",
                        "baseScore": 9.1,
                        "baseSeverity": "CRITICAL",
                        "privilegesRequired": "NONE",
                        "providerUrgency": "NOT_DEFINED",
                        "subAvailabilityImpact": "NONE",
                        "subConfidentialityImpact": "NONE",
                        "subIntegrityImpact": "NONE",
                        "userInteraction": "NONE",
                        "valueDensity": "NOT_DEFINED",
                        "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
                        "version": "4.0",
                        "vulnAvailabilityImpact": "NONE",
                        "vulnConfidentialityImpact": "HIGH",
                        "vulnIntegrityImpact": "HIGH",
                        "vulnerabilityResponseEffort": "NOT_DEFINED"
                    },
                    "format": "CVSS",
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "GENERAL"
                        }
                    ]
                }
            ],
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-295",
                            "description": "CWE-295 Improper Certificate Validation",
                            "lang": "en",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
                "shortName": "EEF",
                "dateUpdated": "2026-10-26T13:49:29.374Z"
            },
            "references": [
                {
                    "name": "Drop the certifi partial_chain when the caller pins cacerts or cacertfile (benoitc/hackney#978)",
                    "tags": [
                        "related"
                    ],
                    "url": "https://github.com/benoitc/hackney/pull/978"
                },
                {
                    "name": "EEF CNA record for CVE-2026-115693",
                    "tags": [
                        "related"
                    ],
                    "url": "https://cna.erlef.org/cves/CVE-2026-115693.html"
                },
                {
                    "name": "OSV record EEF-CVE-2026-115693",
                    "tags": [
                        "related"
                    ],
                    "url": "https://osv.dev/vulnerability/EEF-CVE-2026-115693"
                },
                {
                    "name": "hackney 4.9.0 release notes",
                    "tags": [
                        "vendor-advisory",
                        "related"
                    ],
                    "url": "https://github.com/benoitc/hackney/releases/tag/4.9.0"
                },
                {
                    "name": "Introducing commit d8a9afc in benoitc/hackney",
                    "tags": [
                        "related"
                    ],
                    "url": "https://github.com/benoitc/hackney/commit/d8a9afcf5c3849904274e2eba1df56c63d1a1a0c"
                },
                {
                    "name": "Fix commit 915eb57 in benoitc/hackney",
                    "tags": [
                        "patch"
                    ],
                    "url": "https://github.com/benoitc/hackney/commit/915eb5737e9c489d8fc22eec8cdae30e9b027be4"
                }
            ],
            "source": {
                "discovery": "EXTERNAL"
            },
            "title": "Custom cacerts or cacertfile do not restrict trust to the pinned CA in hackney",
            "workarounds": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>Pass your own <code>{partial_chain, Fun}</code> in <code>ssl_options</code> alongside <code>cacerts</code> or <code>cacertfile</code>. A caller-supplied <code>partial_chain</code> replaces hackney's in the merge, and a callback that returns <code>unknown_ca</code> makes OTP validate against the configured <code>cacerts</code> only.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "Pass your own `{partial_chain, Fun}` in `ssl_options` alongside `cacerts` or `cacertfile`. A caller-supplied `partial_chain` replaces hackney's in the merge, and a callback that returns `unknown_ca` makes OTP validate against the configured `cacerts` only."
                        }
                    ],
                    "value": "Pass your own {partial_chain, Fun} in ssl_options alongside cacerts or cacertfile. A caller-supplied partial_chain replaces hackney's in the merge, and a callback that returns unknown_ca makes OTP validate against the configured cacerts only."
                }
            ],
            "x_technicalAnalysis": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p><strong>1. Default trust options.</strong> <code>hackney_ssl:check_hostname_opts/1</code> builds the <code>verify_peer</code> options for every TLS connection: the certifi <code>cacerts</code>, a hostname <code>verify_fun</code>, and <code>{partial_chain, fun hackney_ssl:partial_chain/1}</code>. The callback walks the peer chain and returns <code>{trusted_ca, Cert}</code> for the first certificate whose public key matches a root in the bundled certifi store, which lets OTP accept chains that end in a cross-signed root.</p>\n<p><strong>2. Merge keeps the callback.</strong> When the caller passes <code>ssl_options</code>, <code>hackney_ssl:merge_ssl_opts/3</code> merges them over the defaults with the caller's values winning per key. <code>cacerts</code> or <code>cacertfile</code> replace the trust store, and a <code>cacertfile</code> removes the default <code>cacerts</code>, but <code>partial_chain</code> has no counterpart in the caller's options and stays.</p>\n<p><strong>3. Validation.</strong> OTP consults <code>partial_chain</code> before the configured trust store. A peer chain that carries any publicly trusted root therefore gets that root as its trust anchor, and the pinned <code>cacerts</code> are never consulted. Only the hostname <code>verify_fun</code> still constrains the attacker.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "**1. Default trust options.** `hackney_ssl:check_hostname_opts/1` builds the `verify_peer` options for every TLS connection: the certifi `cacerts`, a hostname `verify_fun`, and `{partial_chain, fun hackney_ssl:partial_chain/1}`. The callback walks the peer chain and returns `{trusted_ca, Cert}` for the first certificate whose public key matches a root in the bundled certifi store, which lets OTP accept chains that end in a cross-signed root.\n\n**2. Merge keeps the callback.** When the caller passes `ssl_options`, `hackney_ssl:merge_ssl_opts/3` merges them over the defaults with the caller's values winning per key. `cacerts` or `cacertfile` replace the trust store, and a `cacertfile` removes the default `cacerts`, but `partial_chain` has no counterpart in the caller's options and stays.\n\n**3. Validation.** OTP consults `partial_chain` before the configured trust store. A peer chain that carries any publicly trusted root therefore gets that root as its trust anchor, and the pinned `cacerts` are never consulted. Only the hostname `verify_fun` still constrains the attacker."
                        }
                    ],
                    "value": "1. Default trust options. hackney_ssl:check_hostname_opts/1 builds the verify_peer options for every TLS connection: the certifi cacerts, a hostname verify_fun, and {partial_chain, fun hackney_ssl:partial_chain/1}. The callback walks the peer chain and returns {trusted_ca, Cert} for the first certificate whose public key matches a root in the bundled certifi store, which lets OTP accept chains that end in a cross-signed root.\n\n2. Merge keeps the callback. When the caller passes ssl_options, hackney_ssl:merge_ssl_opts/3 merges them over the defaults with the caller's values winning per key. cacerts or cacertfile replace the trust store, and a cacertfile removes the default cacerts, but partial_chain has no counterpart in the caller's options and stays.\n\n3. Validation. OTP consults partial_chain before the configured trust store. A peer chain that carries any publicly trusted root therefore gets that root as its trust anchor, and the pinned cacerts are never consulted. Only the hostname verify_fun still constrains the attacker."
                }
            ]
        }
    }
}