{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-99042", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.387Z", "datePublished": "2026-10-23T12:22:01.804Z", "dateUpdated": "2026-10-24T14:10:09.161Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:10:09.161Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6\n\nio_connect_bpf_populate() fills connect.port and connect.v6_addr for\nAF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28\nbytes.\n\nThe IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which\nalready holds sin6_port and sin6_addr. io_connect() passes addr_len to\nthe socket layer unchanged.\n\nAt addr_len 24 the filter sees family AF_INET6 with port and address\nzero, while the kernel connects to the real destination. A filter that\ndenies an IPv6 port or address is bypassed. Denying connect.port == P\nrejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24.\n\nUse SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when\nabsent.\n\nThe threshold mismatch was found by an AI coding assistant (Claude Code)\ncomparing this hook against the net/ipv6 length checks on my\ninstructions; it also drafted the reproducer and this patch. I verified\nthe bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same\ncode." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N", "baseScore": 8.4, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - An attacker reaches the patched io_connect_bpf_populate() by locally submitting IORING_OP_CONNECT through io_uring_enter(), with sqe->addr2 supplying the malicious 24-byte length. No network packet carries the value creating the mismatch.\nAC:L - Against a CONNECT filter denying an IPv6 port or address, addr2=24 deterministically makes io_connect_bpf_populate() expose zero port/address while tcp_v6_connect() accepts and uses the real fields; no race or uncontrolled condition is involved.\nPR:L - No capability check exists in io_uring_enter(), io_connect_prep(), or io_connect(), and AF_INET6 SOCK_STREAM creation avoids inet6_create()'s CAP_NET_RAW check. An ordinary confined process with access to the filtered ring can trigger the bypass.\nUI:N - The confined process prepares and submits the 24-byte sockaddr itself, and io_connect_prep() copies it during io_uring_enter(); no other user must mount, open, approve, or otherwise act.\nS:C - The false port/address view escapes the io_uring BPF CONNECT sandbox: __io_uring_run_bpf_filters() allows an operation that an inherited or ring-level filter intended to deny, reaching network resources outside that policy scope.\nC:H - After the filter sees :: and port 0, tcp_v6_connect() uses sin6_addr and sin6_port from the same 24 bytes; the confined process can establish a full socket and read responses from IPv6 services the CONNECT filter explicitly made inaccessible.\nI:H - tcp_v6_connect() stores the hidden destination in sk_v6_daddr and inet_dport and establishes the denied socket, enabling arbitrary application data and requests to be sent to IPv6 services and ports prohibited by the sandbox policy.\nA:N - The bug only substitutes zero values in the filter context; move_addr_to_kernel() safely copies 24 bytes and the IPv6 socket layer accepts that size. It introduces no corruption, out-of-bounds access, oops, hang, or resource exhaustion." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "io_uring/net.c" ], "versions": [ { "version": "899bea8248cee35d54760a5e7d61a76af8e64411", "lessThan": "596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5", "status": "affected", "versionType": "git" }, { "version": "899bea8248cee35d54760a5e7d61a76af8e64411", "lessThan": "aa5d5f8e502318e783545ba5d04bb40130b83e20", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "io_uring/net.c" ], "versions": [ { "version": "7.2", "status": "affected" }, { "version": "0", "lessThan": "7.2", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.11", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.2", "versionEndExcluding": "7.2.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.2", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5" }, { "url": "https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20" } ], "title": "io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6", "x_generator": { "engine": "bippy-1.2.0" } } } }