{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89537", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.721Z", "datePublished": "2026-09-11T19:44:15.216Z", "dateUpdated": "2026-10-21T12:47:45.860Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:47:45.860Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_v2\n\ngss_krb5_verify_mic_v2() reads the token ID at ptr[0..1], the flags\nbyte at ptr[2], and padding at ptr[3..7], then passes\nptr + GSS_KRB5_TOK_HDR_LEN and cksum_len to gss_krb5_mic_build_sg().\nNone of these accesses check read_token->len first.\n\nThe minimum safe token size is GSS_KRB5_TOK_HDR_LEN (16) plus\nctx->krb5e->cksum_len (12-24, depending on the enctype). All callers\naccept shorter tokens from the wire:\n\n - gss_unwrap_resp_integ() enforces only an upper bound\n (offset + len <= rcv_buf->len) before allocating\n mic.data = kmalloc(len) and passing it to gss_verify_mic().\n A malicious NFS server can therefore supply a short checksum\n opaque, producing a small slab allocation that the Kerberos MIC\n verifier reads past.\n\n - gss_validate() enforces only len <= RPC_MAX_AUTH_SIZE (400)\n before passing the wire-supplied length to\n gss_validate_seqno_mic(), which constructs a mic xdr_netobj\n and calls gss_verify_mic().\n\n - svcauth_gss_verify_header() enforces only\n checksum.len >= XDR_UNIT (4 bytes) before dispatching to\n gss_verify_mic().\n\n - svcauth_gss_unwrap_integ() checks only that the checksum fits\n in gsd->gsd_scratch.\n\nAdd a length guard at the top of gss_krb5_verify_mic_v2(), before any\nptr[] access or scatterlist construction. Well-formed MIC tokens from\ngss_krb5_get_mic_v2() already have exactly GSS_KRB5_TOK_HDR_LEN +\ncksum_len bytes, so valid traffic is unaffected." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 9.1, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - gss_krb5_verify_mic_v2() is reached from nfsd RPCSEC_GSS on TCP/2049 (svcauth_gss_accept → svcauth_gss_verify_header/unwrap_integ) and from the NFS client processing a remote server's RPCSEC_GSS verifier or krb5i checksum, so a remote peer triggers it with crafted SUNRPC traffic.\nAC:L - A single RPCSEC_GSS Call or Reply with a MIC/checksum shorter than GSS_KRB5_TOK_HDR_LEN plus cksum_len (callers accept as little as 4 bytes) deterministically over-reads; no race or attacker-uncontrollable layout is required. Kerberized NFS is a standard enterprise deployment.\nPR:N - svcauth_gss_verify_header() is the MIC check itself and runs before credentials are verified; the only gate is an rsc-cache lookup on a cleartext, monotonically increasing 64-bit GSS handle that an unauthenticated client can sniff or enumerate. A malicious NFS server needs no privileges on the client.\nUI:N - On nfsd the over-read is triggered solely by an inbound RPCSEC_GSS message; on the client it fires from the RPC receive path once an NFS/RPCSEC_GSS mount exists. No separate victim action is required at attack time.\nS:U - The slab over-read and any resulting oops stay inside the host kernel SUNRPC/GSS code. This is ordinary same-host kernel impact, not a VM escape, IOMMU bypass, or other changed-scope boundary.\nC:H - gss_unwrap_resp_integ() kmallocs only the attacker-chosen checksum length, then gss_krb5_verify_mic_v2() reads GSS_KRB5_TOK_HDR_LEN+cksum_len (28-40) bytes via gss_krb5_mic_build_sg()/sg_pcopy_to_buffer, an out-of-bounds read of adjacent slab well beyond a few bytes.\nI:N - The defect is a read-only over-read consumed as a MIC comparison; rfc3961_verify_mic copies those bytes into a local buffer and memcmp()s them. There is no out-of-bounds write, use-after-free, or control-flow hijack primitive.\nA:H - Reading 28-40 bytes past a small kmalloc object or past an RPC receive buffer near a page boundary can oops or panic on KASAN, redzone, or unmapped next-page kernels, and the attacker can repeat the crafted RPC to deny NFS service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sunrpc/auth_gss/gss_krb5_unseal.c" ], "versions": [ { "version": "de9c17eb4a912c9028f7b470eb80815144883b26", "lessThan": "b2e9e10f5a536befcdce64d3e6946dff42fb823e", "status": "affected", "versionType": "git" }, { "version": "de9c17eb4a912c9028f7b470eb80815144883b26", "lessThan": "997577c52487181226775db3755079a3ba1d52b9", "status": "affected", "versionType": "git" }, { "version": "de9c17eb4a912c9028f7b470eb80815144883b26", "lessThan": "996dd15f60121bdd7896b4554458f8806d608063", "status": "affected", "versionType": "git" }, { "version": "de9c17eb4a912c9028f7b470eb80815144883b26", "lessThan": "7a946b2e7207f968902f2147ab9b30726f82f7ab", "status": "affected", "versionType": "git" }, { "version": "de9c17eb4a912c9028f7b470eb80815144883b26", "lessThan": "b94f6719dcd9f7a609bc5f459f85795900e77d25", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sunrpc/auth_gss/gss_krb5_unseal.c" ], "versions": [ { "version": "2.6.35", "status": "affected" }, { "version": "0", "lessThan": "2.6.35", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.114", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "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": "2.6.35", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.12.114" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b2e9e10f5a536befcdce64d3e6946dff42fb823e" }, { "url": "https://git.kernel.org/stable/c/997577c52487181226775db3755079a3ba1d52b9" }, { "url": "https://git.kernel.org/stable/c/996dd15f60121bdd7896b4554458f8806d608063" }, { "url": "https://git.kernel.org/stable/c/7a946b2e7207f968902f2147ab9b30726f82f7ab" }, { "url": "https://git.kernel.org/stable/c/b94f6719dcd9f7a609bc5f459f85795900e77d25" } ], "title": "SUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_v2", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89537", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:23:15.980324Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:41.729Z" } } ] } }