{"id":"CVE-2026-31641","summary":"rxrpc: Fix RxGK token loading to check bounds","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Fix RxGK token loading to check bounds\n\nrxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length\nfrom the XDR token as u32 values and passes each through round_up(x, 4)\nbefore using the rounded value for validation and allocation.  When the raw\nlength is \u003e= 0xfffffffd, round_up() wraps to 0, so the bounds check and\nkzalloc both use 0 while the subsequent memcpy still copies the original\n~4 GiB value, producing a heap buffer overflow reachable from an\nunprivileged add_key() call.\n\nFix this by:\n\n (1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket\n     lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with\n     the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX.\n\n (2) Sizing the flexible-array allocation from the validated raw key\n     length via struct_size_t() instead of the rounded value.\n\n (3) Caching the raw lengths so that the later field assignments and\n     memcpy calls do not re-read from the token, eliminating a class of\n     TOCTOU re-parse.\n\nThe control path (valid token with lengths within bounds) is unaffected.","modified":"2026-06-18T03:55:38.653149893Z","published":"2026-04-24T14:44:56.204Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31641.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3e04596cba8a86cbff9c3f4bf0a524a3a488773c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/49875b360c2b83a3c226e189c502e501d83e6445"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d179a868dd755b0cfcf7582e00943d702b9943b8"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31641.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31641"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0ca100ff4df64f5d0f6c1dd5080c3e096786bea6"},{"fixed":"3e04596cba8a86cbff9c3f4bf0a524a3a488773c"},{"fixed":"49875b360c2b83a3c226e189c502e501d83e6445"},{"fixed":"d179a868dd755b0cfcf7582e00943d702b9943b8"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31641.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.16.0"},{"fixed":"6.18.23"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.13"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31641.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}