{ "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" } } } }