{"api_version":"1","generated_at":"2026-09-12T11:23:59+00:00","cve":"CVE-2026-89537","urls":{"html":"https://cve.report/CVE-2026-89537","api":"https://cve.report/api/cve/CVE-2026-89537.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89537","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89537"},"summary":{"title":"SUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_v2","description":"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:36","updated_at":"2026-09-11 20:19:36"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/7a946b2e7207f968902f2147ab9b30726f82f7ab","name":"https://git.kernel.org/stable/c/7a946b2e7207f968902f2147ab9b30726f82f7ab","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b94f6719dcd9f7a609bc5f459f85795900e77d25","name":"https://git.kernel.org/stable/c/b94f6719dcd9f7a609bc5f459f85795900e77d25","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89537","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89537","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected de9c17eb4a912c9028f7b470eb80815144883b26 7a946b2e7207f968902f2147ab9b30726f82f7ab git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected de9c17eb4a912c9028f7b470eb80815144883b26 b94f6719dcd9f7a609bc5f459f85795900e77d25 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2.6.35","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 2.6.35 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/sunrpc/auth_gss/gss_krb5_unseal.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"7a946b2e7207f968902f2147ab9b30726f82f7ab","status":"affected","version":"de9c17eb4a912c9028f7b470eb80815144883b26","versionType":"git"},{"lessThan":"b94f6719dcd9f7a609bc5f459f85795900e77d25","status":"affected","version":"de9c17eb4a912c9028f7b470eb80815144883b26","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/sunrpc/auth_gss/gss_krb5_unseal.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"2.6.35"},{"lessThan":"2.6.35","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"2.6.35","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"2.6.35","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:44:15.216Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89537","datePublished":"2026-09-11T19:44:15.216Z","dateReserved":"2026-09-11T19:38:34.721Z","dateUpdated":"2026-09-11T19:44:15.216Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:36","lastModifiedDate":"2026-09-11 20:19:36","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89537","Ordinal":"1","Title":"SUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_","CVE":"CVE-2026-89537","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89537","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"SUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_"}]}}}