{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21796", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.768Z", "datePublished": "2025-02-27T02:18:32.191Z", "dateUpdated": "2026-08-05T11:54:31.388Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:54:31.388Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: clear acl_access/acl_default after releasing them\n\nIf getting acl_default fails, acl_access and acl_default will be released\nsimultaneously. However, acl_access will still retain a pointer pointing\nto the released posix_acl, which will trigger a WARNING in\nnfs3svc_release_getacl like this:\n\n------------[ cut here ]------------\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 26 PID: 3199 at lib/refcount.c:28\nrefcount_warn_saturate+0xb5/0x170\nModules linked in:\nCPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted\n6.12.0-rc6-00079-g04ae226af01f-dirty #8\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS\n1.16.1-2.fc37 04/01/2014\nRIP: 0010:refcount_warn_saturate+0xb5/0x170\nCode: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75\ne4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb\ncd 0f b6 1d 8a3\nRSP: 0018:ffffc90008637cd8 EFLAGS: 00010282\nRAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde\nRDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380\nRBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56\nR10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001\nR13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0\nFS: 0000000000000000(0000) GS:ffff88871ed00000(0000)\nknlGS:0000000000000000\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \n ? refcount_warn_saturate+0xb5/0x170\n ? __warn+0xa5/0x140\n ? refcount_warn_saturate+0xb5/0x170\n ? report_bug+0x1b1/0x1e0\n ? handle_bug+0x53/0xa0\n ? exc_invalid_op+0x17/0x40\n ? asm_exc_invalid_op+0x1a/0x20\n ? tick_nohz_tick_stopped+0x1e/0x40\n ? refcount_warn_saturate+0xb5/0x170\n ? refcount_warn_saturate+0xb5/0x170\n nfs3svc_release_getacl+0xc9/0xe0\n svc_process_common+0x5db/0xb60\n ? __pfx_svc_process_common+0x10/0x10\n ? __rcu_read_unlock+0x69/0xa0\n ? __pfx_nfsd_dispatch+0x10/0x10\n ? svc_xprt_received+0xa1/0x120\n ? xdr_init_decode+0x11d/0x190\n svc_process+0x2a7/0x330\n svc_handle_xprt+0x69d/0x940\n svc_recv+0x180/0x2d0\n nfsd+0x168/0x200\n ? __pfx_nfsd+0x10/0x10\n kthread+0x1a2/0x1e0\n ? kthread+0xf4/0x1e0\n ? __pfx_kthread+0x10/0x10\n ret_from_fork+0x34/0x60\n ? __pfx_kthread+0x10/0x10\n ret_from_fork_asm+0x1a/0x30\n \nKernel panic - not syncing: kernel: panic_on_warn set ...\n\nClear acl_access/acl_default after posix_acl_release is called to prevent\nUAF from being triggered." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable functions are the NFSACL sideband RPC handlers (program 100227, ACLPROC2/3_GETACL) served by the in-kernel nfsd on port 2049; a remote NFS client reaches them purely by sending a GETACL call with a filehandle and a mask.\nAC:L - The attacker fully controls the mask field that selects both the access and default ACL branches, and can retry indefinitely; the error condition is deterministic on FUSE-backed exports and on any file with a malformed/corrupt system.posix_acl_default xattr, and is otherwise reachable via the unlocked -ERANGE window in ext4_get_acl that the attacker drives from both sides with concurrent SETACL/GETACL.\nPR:N - NFS AUTH_SYS performs no real authentication — the client merely asserts a uid — and fh_verify() is called with NFSD_MAY_NOP, so nfsd_permission() returns 0 without any file ownership or mode check; any host permitted by the export list can issue GETACL against any object in the export.\nUI:N - The entire sequence is driven by attacker-sent RPC calls handled by the nfsd kernel threads; no action by a local user or administrator is required.\nS:U - The freed posix_acl, the dangling inode->i_acl, and the resulting corruption all reside in the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - In the NFSv2-ACL encoder the released posix_acl is still passed to nfs_stream_encode_acl(), which reads a_count and up to 1024 a_entries[] from the freed slab object and transmits them to the remote client, yielding freed-heap disclosure plus a large out-of-bounds read; the cached-ACL variant additionally leaves inode->i_acl dangling for later reads.\nI:H - The second posix_acl_release() performs an atomic decrement into freed (potentially reallocated) slab memory, and in the cached case the dangling inode->i_acl leads to refcount_inc on freed memory, a genuine double free on the next set/forget_cached_acl, and posix_acl_permission() making file access-control decisions from attacker-groomable freed heap contents.\nA:H - The bug reproduces as a refcount_t underflow WARN in nfs3svc_release_getacl (kernel panic with panic_on_warn, as shown in the commit's own report), and the use-after-free of a slab object causes further corruption and oopses; it is remotely and repeatedly triggerable." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs2acl.c", "fs/nfsd/nfs3acl.c" ], "versions": [ { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "8a1737ae42c928384ab6447f6ee1a882510e85fa", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "6f7cfee1a316891890c505563aa54f3476db52fd", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "2e59b2b68782519560b3d6a41dd66a3d01a01cd3", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "55d947315fb5f67a35e4e1d3e01bb886b9c6decf", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "f8d871523142f7895f250a856f8c4a4181614510", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "1fd94884174bd20beb1773990fd3b1aa877688d9", "status": "affected", "versionType": "git" }, { "version": "a257cdd0e2179630d3201c32ba14d7fcb3c3a055", "lessThan": "7faf14a7b0366f153284db0ad3347c457ea70136", "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/nfs2acl.c", "fs/nfsd/nfs3acl.c" ], "versions": [ { "version": "2.6.13", "status": "affected" }, { "version": "0", "lessThan": "2.6.13", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.235", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.179", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.129", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.79", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.16", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13.4", "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": "2.6.13", "versionEndExcluding": "5.10.235" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "5.15.179" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "6.1.129" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "6.6.79" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "6.12.16" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "6.13.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.13", "versionEndExcluding": "6.14" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/8a1737ae42c928384ab6447f6ee1a882510e85fa" }, { "url": "https://git.kernel.org/stable/c/6f7cfee1a316891890c505563aa54f3476db52fd" }, { "url": "https://git.kernel.org/stable/c/2e59b2b68782519560b3d6a41dd66a3d01a01cd3" }, { "url": "https://git.kernel.org/stable/c/55d947315fb5f67a35e4e1d3e01bb886b9c6decf" }, { "url": "https://git.kernel.org/stable/c/f8d871523142f7895f250a856f8c4a4181614510" }, { "url": "https://git.kernel.org/stable/c/1fd94884174bd20beb1773990fd3b1aa877688d9" }, { "url": "https://git.kernel.org/stable/c/7faf14a7b0366f153284db0ad3347c457ea70136" } ], "title": "nfsd: clear acl_access/acl_default after releasing them", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "cvssV3_1": { "scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH" } }, { "other": { "type": "ssvc", "content": { "id": "CVE-2025-21796", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2025-02-27T17:57:11.080279Z" } } } ], "problemTypes": [ { "descriptions": [ { "lang": "en", "type": "CWE", "cweId": "CWE-416", "description": "CWE-416 Use After Free" } ] } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-02-27T18:02:26.612Z" } }, { "title": "CVE Program Container", "references": [ { "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html" }, { "url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T20:59:40.254Z" } }, { "x_adpType": "supplier", "providerMetadata": { "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "shortName": "siemens-SADP", "dateUpdated": "2026-07-14T12:40:10.487Z" }, "affected": [ { "vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "versions": [ { "status": "affected", "version": "V3.1.5", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "versions": [ { "status": "affected", "version": "V3.1.6", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "versions": [ { "status": "affected", "version": "V3.1.5", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "versions": [ { "status": "affected", "version": "V3.1.6", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP", "versions": [ { "status": "affected", "version": "V3.1.5", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": 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