{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89664", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.745Z", "datePublished": "2026-09-11T19:45:51.319Z", "dateUpdated": "2026-10-19T08:50:35.770Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:35.770Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: release OPEN-decoded posix ACLs via op_release\n\nnfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates\nrefcounted struct posix_acl objects via posix_acl_alloc() and stores\nthem in open->op_pacl and open->op_dpacl. These pointers must be\nreleased once the OPEN compound finishes.\n\nWhen nfsd4_decode_open_claim4() returns a non-seqid-mutating error,\nthe dispatcher short-circuits before op_func runs:\n\n nfsd4_proc_compound()\n if (op->status && op->opnum == OP_OPEN)\n op->status = nfsd4_open_omfg(...)\n if (!seqid_mutating_err(ntohl(op->status)))\n return op->status; /* nfsd4_open() never runs */\n ...\n opdesc->op_release(&op->u) /* must still release op_pacl/op_dpacl */\n\nBefore this change OP_OPEN had no .op_release in nfsd4_ops[], and the\nrelease pair lived inside nfsd4_open() at its out_err: label. On the\nshort-circuit path nfsd4_open() is never invoked, so both posix_acl\nrefs leak on every malformed OPEN compound that carries valid POSIX\nACL createhow4 attributes.\n\nAdd nfsd4_open_release() and wire it as .op_release for OP_OPEN.\nposix_acl_release() is NULL-safe, so the single release site covers\nboth the normal path and the nfsd4_open_omfg short-circuit. Remove\nthe matching posix_acl_release() pair from nfsd4_open()'s out_err:\nlabel to avoid double-releasing.\n\nThe compound loop has two encoding branches: nfsd4_encode_operation()\nfor normal ops, and nfsd4_encode_replay() for v4.0 replayed ops.\nop_release was only called from nfsd4_encode_operation(), so resources\nattached to op->u leak on the replay path.\n\nMove the op_release() call out of nfsd4_encode_operation() and the\nreplay branch, placing it after the if-else in nfsd4_proc_compound().\nThis gives a single call site in a fairly obviously-correct place,\ncovering both the normal encoding and replay paths." } ], "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 leak is in nfsd NFSv4 OPEN XDR decoding (nfsd4_decode_createhow4 → nfsd4_decode_fattr4 → posix_acl_alloc), reached over the network via COMPOUND RPCs on TCP/UDP port 2049 when the in-kernel NFS server is running.\nAC:L - An attacker can deterministically leak the ACLs by sending OPEN with CREATE and valid POSIX ACL attributes, then a non-seqid-mutating decode error such as NFS4ERR_BADXDR on open_claim4, so nfsd4_open() never runs; no race or luck is required.\nPR:N - OPEN decode allocates the posix_acl objects after spoofable RPC AUTH_UNIX and before nfsd4_open(), fh_verify(), export permission checks, or clientid/session validation, so no authenticated NFS identity or local account on the server is required.\nUI:N - The attacker triggers the leak solely by sending crafted NFSv4 COMPOUND packets; no victim user must mount a filesystem, open a file, or take any other action.\nS:U - Impact is confined to kernel slab consumption on the NFS server host and does not cross a VM, guest, sandbox, or IOMMU security boundary.\nC:N - This is a refcount leak of attacker-supplied posix_acl allocations with no out-of-bounds read, use-after-free, or other primitive that could disclose kernel or file data.\nI:N - The short-circuit path never runs nfsd4_open() or writes file/ACL metadata; the only effect is orphaned kmalloc objects, with no memory corruption or unauthorized modification.\nA:H - Each malformed OPEN permanently leaks up to two posix_acl objects (NFS_ACL_MAX_ENTRIES=1024, about 16KB each) for the server lifetime; repeating the request exhausts kernel memory and can OOM the NFS server and co-hosted workloads." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4proc.c", "fs/nfsd/nfs4xdr.c" ], "versions": [ { "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "lessThan": "5b3a7d7c23c071efe12dd1bc1d2e5f97c4892921", "status": "affected", "versionType": "git" }, { "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "lessThan": "8215892993ea9f5231da4fa9eb42428a286fce8b", "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/nfs4proc.c", "fs/nfsd/nfs4xdr.c" ], "versions": [ { "version": "7.0", "status": "affected" }, { "version": "0", "lessThan": "7.0", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "7.0", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/5b3a7d7c23c071efe12dd1bc1d2e5f97c4892921" }, { "url": "https://git.kernel.org/stable/c/8215892993ea9f5231da4fa9eb42428a286fce8b" } ], "title": "nfsd: release OPEN-decoded posix ACLs via op_release", "x_generator": { "engine": "bippy-1.2.0" } } } }