{"cve":"CVE-2026-89541","nvd":{"published":"2026-09-11T20:19:37.247","modified":"2026-10-19T09:17:48.983","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: harden gss_unwrap_resp_priv length checks\n\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\n\n    offset = (u8 *)(p) - (u8 *)head->iov_base;\n    if (offset + opaque_len > rcv_buf->len)\n            goto unwrap_failed;\n    maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset,\n                          offset + opaque_len, rcv_buf);\n\nBoth operands are u32 and the sum is computed in u32. A reply with\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\nvalue that is below rcv_buf->len, so the bound check passes and\ngss_unwrap() is called with end < begin. The check also lacks a\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\nheader reads at ptr+4 and ptr+6 then run past the token.\n\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\nrotate_left() loop that follows.\n\nFix by replacing the single combined check with three guards that\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\nouter token length:\n\n    if (offset > rcv_buf->len)\n            goto unwrap_failed;\n    if (opaque_len > rcv_buf->len - offset)\n            goto unwrap_failed;\n    if (opaque_len < GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;\n\nThe first guard makes the subtraction in the second guard\nunconditionally safe; offset is derived from a successful\nxdr_inline_decode() in the head kvec, so in practice it already\nsatisfies the bound. The floor mirrors the server-side check added\nin commit 5b757c2e57a5 (\"SUNRPC: svcauth_gss: enforce krb5 token\nminimum length\").","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":[],"references":["https://git.kernel.org/stable/c/3691c4b3488d8ca046b9941e5be30c626dbbbb50","https://git.kernel.org/stable/c/401f6a5b338d05bb1069ad814d9f77e3c367854f","https://git.kernel.org/stable/c/81fd7654a8429718adfcb2a7e03496077f547ed0","https://git.kernel.org/stable/c/85fa6b12e8f439739ac36ef2aad925f37c8b976a","https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-89541","score":0.00514,"percentile":0.43523,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}