{"cve":"CVE-2026-89538","nvd":{"published":"2026-09-11T20:19:36.850","modified":"2026-10-19T09:17:48.573","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: Reject krb5 v2 wrap tokens with oversized ec field\n\ngss_krb5_unwrap_v2() sets buf->len to a logical\nlength, which can be much smaller than head[0].iov_len\n(the allocated receive-page capacity).  It then calls\nxdr_buf_trim() with a trim length derived from the 16-bit\n\"extra count\" (ec) field in the Kerberos v2 token header.\n\nThe ec field is authenticated by the post-decrypt memcmp()\nagainst the encrypted header copy, so a randomly-mutated\nvalue is rejected.  However, any peer holding a valid GSS\ncontext can legitimately encrypt a token whose ec exceeds\nthe plaintext length.  Per RFC 4121, such a token is\nstructurally malformed.\n\nAlthough xdr_buf_trim() now clamps the buf->len subtraction\nto avoid unsigned underflow, the buffer is still left in a\nsemantically invalid state (zero length, inconsistent iov\nlengths) when ec is oversized.\n\nReject these tokens before calling xdr_buf_trim(), giving\ncallers a well-defined GSS_S_DEFECTIVE_TOKEN error and\nkeeping the xdr_buf internally consistent.  The wrapped blob\nbegins at a nonzero offset -- both callers pass len as\noffset + opaque_len -- so buf->len still counts the offset\nbytes that precede the blob.  Compare the trim length\nagainst the remaining wrapped segment, buf->len - offset,\nrather than the whole buffer; comparing against buf->len\nalone leaves an offset-wide window in which an oversized ec\npasses the test and xdr_buf_trim() cuts into the bytes ahead\nof the blob.","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/1f9856af065b6158271687e9788407b9573fd16f","https://git.kernel.org/stable/c/4abb44a29bb515df6f49123848765c70fc9b5021","https://git.kernel.org/stable/c/880effc943ed82d6811f272ed3307c222b40f4d6","https://git.kernel.org/stable/c/9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296","https://git.kernel.org/stable/c/ac9efc29346b6942e71f0e24a3178a9121330fab"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-89538","score":0.00714,"percentile":0.53394,"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."]}