{"api_version":"1","generated_at":"2026-09-12T03:40:14+00:00","cve":"CVE-2026-89551","urls":{"html":"https://cve.report/CVE-2026-89551","api":"https://cve.report/api/cve/CVE-2026-89551.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89551","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89551"},"summary":{"title":"SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow\n\nxdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by\nwalking the tail, pages, and head iovecs.  Each per-section step\nuses min_t() so it never removes more bytes than that section\nholds, but the final accounting at the fix_len label subtracts the\ntotal bytes actually consumed from buf->len without any clamp:\n\n    fix_len:\n            buf->len -= (len - trim);\n\nWhen the caller has set buf->len to a value smaller than the sum\nof the iov_lens, (len - trim) can exceed buf->len and the unsigned\nsubtraction wraps to near UINT_MAX.  gss_krb5_unwrap_v2() reaches\nxdr_buf_trim() in exactly that state:\n\n    buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;\n    buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);\n    xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);\n\nbuf->len is a small wire-derived value while the iov_lens are at\npage scale, so the per-section loops legitimately consume far more\nbytes than buf->len records.  The wrapped buf->len then propagates\nas the authoritative stream bound into every downstream XDR\ndecoder.\n\nFix by clamping the decrement so buf->len bottoms out at zero:\n\n    buf->len -= min_t(unsigned int, buf->len, len - trim);\n\nOn the normal path where the iov_lens sum to buf->len, (len - trim)\nis always <= buf->len and the result is identical to before.  No\ncallers change behavior outside the underflow case.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:38","updated_at":"2026-09-11 20:19:38"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/e6267cccd7b05cc514e57f2160aa8db85f5c2701","name":"https://git.kernel.org/stable/c/e6267cccd7b05cc514e57f2160aa8db85f5c2701","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ad0cce80d4af2f74674e8b635d97aa3880e83da8","name":"https://git.kernel.org/stable/c/ad0cce80d4af2f74674e8b635d97aa3880e83da8","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3f491306dcb673ff5e78e1044ba450c58978774e","name":"https://git.kernel.org/stable/c/3f491306dcb673ff5e78e1044ba450c58978774e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/85e9602650e9df07190abe817cee3b4d9bc3df17","name":"https://git.kernel.org/stable/c/85e9602650e9df07190abe817cee3b4d9bc3df17","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89551","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89551","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4c190e2f913f038c9c91ee63b59cd037260ba353 e6267cccd7b05cc514e57f2160aa8db85f5c2701 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4c190e2f913f038c9c91ee63b59cd037260ba353 ad0cce80d4af2f74674e8b635d97aa3880e83da8 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4c190e2f913f038c9c91ee63b59cd037260ba353 85e9602650e9df07190abe817cee3b4d9bc3df17 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4c190e2f913f038c9c91ee63b59cd037260ba353 3f491306dcb673ff5e78e1044ba450c58978774e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.9","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.9 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* 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/xdr.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"e6267cccd7b05cc514e57f2160aa8db85f5c2701","status":"affected","version":"4c190e2f913f038c9c91ee63b59cd037260ba353","versionType":"git"},{"lessThan":"ad0cce80d4af2f74674e8b635d97aa3880e83da8","status":"affected","version":"4c190e2f913f038c9c91ee63b59cd037260ba353","versionType":"git"},{"lessThan":"85e9602650e9df07190abe817cee3b4d9bc3df17","status":"affected","version":"4c190e2f913f038c9c91ee63b59cd037260ba353","versionType":"git"},{"lessThan":"3f491306dcb673ff5e78e1044ba450c58978774e","status":"affected","version":"4c190e2f913f038c9c91ee63b59cd037260ba353","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/sunrpc/xdr.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.9"},{"lessThan":"3.9","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","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":"6.12.109","versionStartIncluding":"3.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"3.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"3.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"3.9","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow\n\nxdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by\nwalking the tail, pages, and head iovecs.  Each per-section step\nuses min_t() so it never removes more bytes than that section\nholds, but the final accounting at the fix_len label subtracts the\ntotal bytes actually consumed from buf->len without any clamp:\n\n    fix_len:\n            buf->len -= (len - trim);\n\nWhen the caller has set buf->len to a value smaller than the sum\nof the iov_lens, (len - trim) can exceed buf->len and the unsigned\nsubtraction wraps to near UINT_MAX.  gss_krb5_unwrap_v2() reaches\nxdr_buf_trim() in exactly that state:\n\n    buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;\n    buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);\n    xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);\n\nbuf->len is a small wire-derived value while the iov_lens are at\npage scale, so the per-section loops legitimately consume far more\nbytes than buf->len records.  The wrapped buf->len then propagates\nas the authoritative stream bound into every downstream XDR\ndecoder.\n\nFix by clamping the decrement so buf->len bottoms out at zero:\n\n    buf->len -= min_t(unsigned int, buf->len, len - trim);\n\nOn the normal path where the iov_lens sum to buf->len, (len - trim)\nis always <= buf->len and the result is identical to before.  No\ncallers change behavior outside the underflow case."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:44:25.327Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/e6267cccd7b05cc514e57f2160aa8db85f5c2701"},{"url":"https://git.kernel.org/stable/c/ad0cce80d4af2f74674e8b635d97aa3880e83da8"},{"url":"https://git.kernel.org/stable/c/85e9602650e9df07190abe817cee3b4d9bc3df17"},{"url":"https://git.kernel.org/stable/c/3f491306dcb673ff5e78e1044ba450c58978774e"}],"title":"SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89551","datePublished":"2026-09-11T19:44:25.327Z","dateReserved":"2026-09-11T19:38:34.723Z","dateUpdated":"2026-09-11T19:44:25.327Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:38","lastModifiedDate":"2026-09-11 20:19:38","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89551","Ordinal":"1","Title":"SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow","CVE":"CVE-2026-89551","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89551","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow\n\nxdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by\nwalking the tail, pages, and head iovecs.  Each per-section step\nuses min_t() so it never removes more bytes than that section\nholds, but the final accounting at the fix_len label subtracts the\ntotal bytes actually consumed from buf->len without any clamp:\n\n    fix_len:\n            buf->len -= (len - trim);\n\nWhen the caller has set buf->len to a value smaller than the sum\nof the iov_lens, (len - trim) can exceed buf->len and the unsigned\nsubtraction wraps to near UINT_MAX.  gss_krb5_unwrap_v2() reaches\nxdr_buf_trim() in exactly that state:\n\n    buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;\n    buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);\n    xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);\n\nbuf->len is a small wire-derived value while the iov_lens are at\npage scale, so the per-section loops legitimately consume far more\nbytes than buf->len records.  The wrapped buf->len then propagates\nas the authoritative stream bound into every downstream XDR\ndecoder.\n\nFix by clamping the decrement so buf->len bottoms out at zero:\n\n    buf->len -= min_t(unsigned int, buf->len, len - trim);\n\nOn the normal path where the iov_lens sum to buf->len, (len - trim)\nis always <= buf->len and the result is identical to before.  No\ncallers change behavior outside the underflow case.","Type":"Description","Title":"SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow"}]}}}