{"cve":"CVE-2026-89550","nvd":{"published":"2026-09-11T20:19:38.500","modified":"2026-10-19T09:17:50.253","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: svcauth_gss: enforce krb5 token minimum length\n\nsvcauth_gss_unwrap_priv() validates only an upper bound on the\nwire-supplied opaque length before handing the buffer to\ngss_unwrap():\n\n    if (len > xdr_stream_remaining(xdr))\n            goto unwrap_failed;\n    offset = xdr_stream_pos(xdr);\n    ...\n    maj_stat = gss_unwrap(ctx, offset, offset + len, buf);\n\nThe wire value `len` flows unchanged as the upper bound into the\nkrb5 unwrap path, so a len in [0, 16] passes this check and is\nhanded to gss_unwrap(). For a krb5 v2 context that lands in\ngss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token\nheader fields at ptr+4 and ptr+6 and then calls rotate_left()\nbefore any integrity check. With a sub-header length the header\nreads run past the token, and _rotate_left()'s `shift %= buf->len`\npath can divide by zero when buf->len has been driven to zero by\nthe truncated token. A header-only token (len == 16) is equally\ninvalid: with a non-zero RRC field and the opaque blob ending at\nthe XDR buffer boundary, rotate_left() builds a zero-length\nsubbuffer, reaching the same division.\n\nReject the token at the server entry point before it reaches the\nkrb5 unwrap core. A valid sealed RFC 4121 token must contain\nthe 16-byte header plus at least some encrypted payload.\n\nFix by adding a minimum-length check immediately after the\nexisting upper-bound check:\n\n    if (len <= GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;","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/0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd","https://git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c","https://git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489","https://git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651","https://git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-89550","score":0.00457,"percentile":0.39412,"date":"2026-10-26"},"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."]}