{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40326","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.186Z","datePublished":"2025-12-08T00:46:53.212Z","dateUpdated":"2026-08-05T12:09:38.372Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:09:38.372Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Define actions for the new time_deleg FATTR4 attributes\n\nNFSv4 clients won't send legitimate GETATTR requests for these new\nattributes because they are intended to be used only with CB_GETATTR\nand SETATTR. But NFSD has to do something besides crashing if it\never sees a GETATTR request that queries these attributes.\n\nRFC 8881 Section 18.7.3 states:\n\n> The server MUST return a value for each attribute that the client\n> requests if the attribute is supported by the server for the\n> target file system. If the server does not support a particular\n> attribute on the target file system, then it MUST NOT return the\n> attribute value and MUST NOT set the attribute bit in the result\n> bitmap. The server MUST return an error if it supports an\n> attribute on the target but cannot obtain its value. In that case,\n> no attribute values will be returned.\n\nFurther, RFC 9754 Section 5 states:\n\n> These new attributes are invalid to be used with GETATTR, VERIFY,\n> and NVERIFY, and they can only be used with CB_GETATTR and SETATTR\n> by a client holding an appropriate delegation.\n\nThus there does not appear to be a specific server response mandated\nby specification. Taking the guidance that querying these attributes\nvia GETATTR is \"invalid\", NFSD will return nfserr_inval, failing the\nrequest entirely."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable code is the NFSv4 server (nfsd) XDR encoder, reached purely by processing an NFSv4.2 COMPOUND received over TCP port 2049 from a remote client. No local access to the server is required.\nAC:L - The attacker deterministically triggers the NULL function-pointer call by setting bit 84 or 85 in the GETATTR (or READDIR/VERIFY) attribute bitmap; there is no race, no memory-layout dependency, and the config is the default NFSv4.2 server build.\nPR:N - NFS AUTH_SYS/AUTH_NULL verifies no credentials — the attacker merely issues EXCHANGE_ID/CREATE_SESSION and then PUTROOTFH+GETATTR, with `fh_verify(..., NFSD_MAY_NOP)` performing no permission check, so no authenticated principal is needed against an exported server.\nUI:N - The attacker sends the malformed GETATTR request unilaterally; no action by any administrator or user on the server or on a legitimate client is needed.\nS:U - The crash occurs in the nfsd kernel thread within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - The call to the NULL slot faults before any attribute bytes are encoded and the partial reply is discarded via xdr_truncate_encode(), so no kernel memory contents are disclosed.\nI:N - No out-of-bounds write or type confusion occurs; the indirect call to address 0 faults immediately and a remote attacker cannot map page 0 to gain control flow, so no data or code is modified.\nA:H - Dereferencing the NULL function pointer oopses the nfsd service thread (or panics the machine with panic_on_oops), and the unauthenticated request can be replayed to kill every nfsd thread, taking the file server completely offline."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4xdr.c"],"versions":[{"version":"51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b","lessThan":"d8f3f94dc950e7c62c96af432c26745885b0a18a","status":"affected","versionType":"git"},{"version":"51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b","lessThan":"4f76435fd517981f01608678c06ad9718a86ee98","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4xdr.c"],"versions":[{"version":"6.14","status":"affected"},{"version":"0","lessThan":"6.14","status":"unaffected","versionType":"semver"},{"version":"6.17.8","lessThanOrEqual":"6.17.*","status":"unaffected","versionType":"semver"},{"version":"6.18","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.17.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/d8f3f94dc950e7c62c96af432c26745885b0a18a"},{"url":"https://git.kernel.org/stable/c/4f76435fd517981f01608678c06ad9718a86ee98"}],"title":"NFSD: Define actions for the new time_deleg FATTR4 attributes","x_generator":{"engine":"bippy-1.2.0"}}}}