{"id":"CVE-2026-89542","revision":"9fa2641f1c124e59b46417bfbf9b87f2","records":[{"revision":"9fa2641f1c124e59b46417bfbf9b87f2","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89542","aliases":[],"title":"SUNRPC: harden gss_krb5_unwrap_v2 against short tokens","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: harden gss_krb5_unwrap_v2 against short tokens\n\ngss_krb5_unwrap_v2() reads the EC and RRC header fields at ptr+4 and\nptr+6 before validating that the token is at least GSS_KRB5_TOK_HDR_LEN\n(16) bytes long, and its rotate_left() helper passes buf->len - base\nto xdr_buf_subsegment() without verifying that base <= buf->len. When\na caller hands in a sub-16-byte token, or a token whose declared len\nleaves base past the end of the buffer, three distinct failures follow:\n\n    gss_krb5_unwrap_v2(offset, len, buf)\n      ptr = buf->head[0].iov_base + offset\n      ec  = *(ptr + 4)              /* OOB read on short head */\n      rrc = *(ptr + 6)              /* OOB read on short head */\n      rotate_left(offset + 16, buf, rrc)\n        xdr_buf_subsegment(buf, &subbuf,\n                           base, buf->len - base)   /* u32 wrap when base > len */\n        _rotate_left(&subbuf, shift)\n          shift %= buf->len         /* divide-by-zero when base == len */\n\nAfter decryption, the cleanup arithmetic has the same shape:\n\n    movelen = min_t(unsigned int, buf->head[0].iov_len, len);\n    movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;\n    BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >\n                                            buf->head[0].iov_len);\n\nThe BUG_ON re-adds the value just subtracted, so it reduces to\nmin(A, B) > A and is permanently false; it cannot catch the unsigned\nunderflow of movelen, which then drives a ~UINT_MAX-byte memmove().\n\nAdd four defense-in-depth guards inside the unwrap core so it is safe\nregardless of what its callers validate:\n\n  - reject tokens with len - offset < GSS_KRB5_TOK_HDR_LEN before\n    touching ptr+4/ptr+6;\n  - bail from rotate_left() when buf->len <= base, covering both the\n    underflow and zero-length cases;\n  - return early from _rotate_left() when buf->len is zero, so the\n    shift %= buf->len modulo cannot fault;\n  - replace the dead BUG_ON with a live check that returns\n    GSS_S_DEFECTIVE_TOKEN before the movelen subtraction.","state":0,"publishedAt":"2026-09-11T19:44:18.931+00:00","modifiedAt":"2026-10-19T08:48:33.941+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\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"299d281c7225ded15b28cb861a98d818d82787fc\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"84ddbc8d084c0251d534f14f5d1a7da05be56404\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"075d7cfc4df8c54cb202ba8b28420370c03ba9b6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"f2591660e0eb263c9415bf0d0bb1b111e62df7a4\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"dddcb0f4b7e27fac16a78ea9a1c8ec2e8a241087\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"806584a4b67a7233870c33e5b8f872e76dd02988\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"a7894e10572d53eb10109b8d07459cc8d3435811\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"de9c17eb4a912c9028f7b470eb80815144883b26\",\n                            \"lessThan\": \"6959297aaa9572783d620a226d73c3fb94494888\",\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\": \"2.6.35\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"2.6.35\",\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/299d281c7225ded15b28cb861a98d818d82787fc","https://git.kernel.org/stable/c/84ddbc8d084c0251d534f14f5d1a7da05be56404","https://git.kernel.org/stable/c/075d7cfc4df8c54cb202ba8b28420370c03ba9b6","https://git.kernel.org/stable/c/f2591660e0eb263c9415bf0d0bb1b111e62df7a4","https://git.kernel.org/stable/c/dddcb0f4b7e27fac16a78ea9a1c8ec2e8a241087","https://git.kernel.org/stable/c/806584a4b67a7233870c33e5b8f872e76dd02988","https://git.kernel.org/stable/c/a7894e10572d53eb10109b8d07459cc8d3435811","https://git.kernel.org/stable/c/6959297aaa9572783d620a226d73c3fb94494888"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89542","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89542","identifiers":["CVE-2026-89542"]},"retained":false,"historicalAffected":[]}],"coverage":[]}