{"id":"CVE-2026-89538","revision":"364440ef63524ce29e625ecb327ce8e6","records":[{"revision":"364440ef63524ce29e625ecb327ce8e6","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89538","aliases":[],"title":"SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field","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.","state":0,"publishedAt":"2026-09-11T19:44:15.953+00:00","modifiedAt":"2026-10-19T08:48:29.976+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/sunrpc/auth_gss/gss_krb5_wrap.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"ac9efc29346b6942e71f0e24a3178a9121330fab\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"b5746095b59f4d11f39f08751d36bbdfd1e5deac\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"4abb44a29bb515df6f49123848765c70fc9b5021\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"dfcd81ab45613d45996fbf483d4ef54b0ec90ab9\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"1f9856af065b6158271687e9788407b9573fd16f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"880effc943ed82d6811f272ed3307c222b40f4d6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cf4c024b908353fcc48309374d39e3399d67dfd1\",\n                            \"lessThan\": \"ad484748eec0a66eac0f13ab53b3fbedb7333c91\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/sunrpc/auth_gss/gss_krb5_wrap.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"3.13\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"3.13\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.270\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.221\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.188\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.157\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.109\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.50\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.4\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 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,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/ac9efc29346b6942e71f0e24a3178a9121330fab","https://git.kernel.org/stable/c/b5746095b59f4d11f39f08751d36bbdfd1e5deac","https://git.kernel.org/stable/c/9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296","https://git.kernel.org/stable/c/4abb44a29bb515df6f49123848765c70fc9b5021","https://git.kernel.org/stable/c/dfcd81ab45613d45996fbf483d4ef54b0ec90ab9","https://git.kernel.org/stable/c/1f9856af065b6158271687e9788407b9573fd16f","https://git.kernel.org/stable/c/880effc943ed82d6811f272ed3307c222b40f4d6","https://git.kernel.org/stable/c/ad484748eec0a66eac0f13ab53b3fbedb7333c91"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89538","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89538","identifiers":["CVE-2026-89538"]},"retained":false,"historicalAffected":[]}],"coverage":[]}