{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21900", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.783Z", "datePublished": "2025-04-01T15:26:51.290Z", "dateUpdated": "2026-08-05T11:55:15.442Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:55:15.442Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4: Fix a deadlock when recovering state on a sillyrenamed file\n\nIf the file is sillyrenamed, and slated for delete on close, it is\npossible for a server reboot to triggeer an open reclaim, with can again\nrace with the application call to close(). When that happens, the call\nto put_nfs_open_context() can trigger a synchronous delegreturn call\nwhich deadlocks because it is not marked as privileged.\n\nInstead, ensure that the call to nfs4_inode_return_delegation_on_close()\ncatches the delegreturn, and schedules it asynchronously." } ], "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 - This is NFSv4 client code whose vulnerable path is entered only in response to remote server behaviour — a server reboot/session reset (NFS4ERR_STALE_CLIENTID, NFS4ERR_BAD_SESSION, lease expiry) drives the state manager into open reclaim, and the blocking DELEGRETURN is an RPC to that server. A malicious or compromised NFS server, or an on-path attacker on a typical AUTH_SYS mount, can force state recovery at will over the network.\nAC:L - This is not a tight instruction-level race: the state manager holds the open-context reference across a full OPEN reclaim round trip whose duration the server chooses, and it can be stretched further with NFS4ERR_DELAY/NFS4ERR_GRACE, so the attacker controls the window width and can force recovery repeatedly until the race lands. The other side — an open, unlinked (sillyrenamed) file being closed — is ubiquitous in normal workloads (tmpfile(), mkstemp+unlink, editors, build systems, mail spools).\nPR:N - The attacker is the remote NFS server (or an on-path attacker) and needs no credentials or account on the victim client; the mount is a pre-existing deployment condition. Even under a purely local framing this would only require an unprivileged user, so no elevated privilege is needed on any path.\nUI:N - No human action is required — the attacker forces state recovery, and the sillyrename/close side is satisfied by ordinary background filesystem activity already running on the client.\nS:U - The deadlock is confined to the NFS client kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - This is purely a lock/RPC-ordering deadlock with no memory corruption, out-of-bounds access, or uninitialized data exposure. No information is disclosed to the attacker.\nI:N - No attacker-controlled data modification occurs; nothing is written out of bounds and no state is corrupted in an attacker-directed way. The pending silly-delete simply never completes.\nA:H - The NFSv4 state manager kthread deadlocks permanently with the session slot table left in the draining state, so every subsequent NFSv4 RPC to that server blocks forever — all processes touching any mount from that nfs_client hang unkillably in D state, umount and clean shutdown wedge, and recovery requires a hard reboot. On NFS-root systems (diskless workstations, HPC nodes, thin clients, embedded controllers) this hangs the entire machine." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfs/delegation.c", "fs/nfs/delegation.h", "fs/nfs/nfs4proc.c" ], "versions": [ { "version": "adb4b42d19aea91826621a8d0bac94cf2c08f8bc", "lessThan": "4fe4ae6c2e01d028856b73b6328b12b8945df871", "status": "affected", "versionType": "git" }, { "version": "adb4b42d19aea91826621a8d0bac94cf2c08f8bc", "lessThan": "f41a60bc43e7abbc636fee78bed0d74c31e738b0", "status": "affected", "versionType": "git" }, { "version": "adb4b42d19aea91826621a8d0bac94cf2c08f8bc", "lessThan": "8f8df955f078e1a023ee55161935000a67651f38", "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/nfs/delegation.c", "fs/nfs/delegation.h", "fs/nfs/nfs4proc.c" ], "versions": [ { "version": "6.11", "status": "affected" }, { "version": "0", "lessThan": "6.11", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.18", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13.6", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14", "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": "6.11", "versionEndExcluding": "6.12.18" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.13.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.14" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4fe4ae6c2e01d028856b73b6328b12b8945df871" }, { "url": "https://git.kernel.org/stable/c/f41a60bc43e7abbc636fee78bed0d74c31e738b0" }, { "url": "https://git.kernel.org/stable/c/8f8df955f078e1a023ee55161935000a67651f38" } ], "title": "NFSv4: Fix a deadlock when recovering state on a sillyrenamed file", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "problemTypes": [ { "descriptions": [ { "type": "CWE", "cweId": "CWE-667", "lang": "en", "description": "CWE-667 Improper Locking" } ] } ], "metrics": [ { "cvssV3_1": { "scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE" } }, { "other": { "type": "ssvc", "content": { "timestamp": "2025-10-01T17:18:02.848036Z", "id": "CVE-2025-21900", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-10-01T17:18:05.662Z" } } ] } }