{
  "threat_severity" : "Moderate",
  "public_date" : "2025-02-27T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: nfsd: clear acl_access/acl_default after releasing them",
    "id" : "2348584",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2348584"
  },
  "cvss3" : {
    "cvss3_base_score" : "5.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
    "status" : "verified"
  },
  "cwe" : "CWE-416",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnfsd: clear acl_access/acl_default after releasing them\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------------[ 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<TASK>\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\nnfs3svc_release_getacl+0xc9/0xe0\nsvc_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\nsvc_process+0x2a7/0x330\nsvc_handle_xprt+0x69d/0x940\nsvc_recv+0x180/0x2d0\nnfsd+0x168/0x200\n? __pfx_nfsd+0x10/0x10\nkthread+0x1a2/0x1e0\n? kthread+0xf4/0x1e0\n? __pfx_kthread+0x10/0x10\nret_from_fork+0x34/0x60\n? __pfx_kthread+0x10/0x10\nret_from_fork_asm+0x1a/0x30\n</TASK>\nKernel panic - not syncing: kernel: panic_on_warn set ...\nClear acl_access/acl_default after posix_acl_release is called to prevent\nUAF from being triggered." ],
  "statement" : "A missing pointer reset in NFS ACL error handling led to use-after-free when releasing already-freed ACLs. This could trigger kernel panic via refcount underflow when handling ACL requests in NFSv3.",
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "release_date" : "2025-11-11T00:00:00Z",
    "advisory" : "RHSA-2025:20095",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10.1",
    "package" : "kernel-0:6.12.0-124.8.1.el10_1"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2025-11-11T00:00:00Z",
    "advisory" : "RHSA-2025:20518",
    "cpe" : "cpe:/a:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-611.5.1.el9_7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2025-11-11T00:00:00Z",
    "advisory" : "RHSA-2025:20518",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-611.5.1.el9_7"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Will not fix",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2025-21796\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21796\nhttps://lore.kernel.org/linux-cve-announce/2025022610-CVE-2025-21796-0133@gregkh/T" ],
  "name" : "CVE-2025-21796",
  "csaw" : false
}