CVE-2025-21796

HIGH EPSS 12.7%
Published Feb 27, 20251y ago · Modified Jun 17, 20262w ago
7.8 CVSS 3.1
High
Find Similar
Published Feb 27, 2025 1y ago
Last Modified Jun 17, 2026 2w ago

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: clear acl_access/acl_default after releasing them If getting acl_default fails, acl_access and acl_default will be released simultaneously. However, acl_access will still retain a pointer pointing to the released posix_acl, which will trigger a WARNING in nfs3svc_release_getacl like this: ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 26 PID: 3199 at lib/refcount.c:28 refcount_warn_saturate+0xb5/0x170 Modules linked in: CPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted 6.12.0-rc6-00079-g04ae226af01f-dirty #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb5/0x170 Code: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75 e4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb cd 0f b6 1d 8a3 RSP: 0018:ffffc90008637cd8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380 RBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56 R10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001 R13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0 FS: 0000000000000000(0000) GS:ffff88871ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? refcount_warn_saturate+0xb5/0x170 ? __warn+0xa5/0x140 ? refcount_warn_saturate+0xb5/0x170 ? report_bug+0x1b1/0x1e0 ? handle_bug+0x53/0xa0 ? exc_invalid_op+0x17/0x40 ? asm_exc_invalid_op+0x1a/0x20 ? tick_nohz_tick_stopped+0x1e/0x40 ? refcount_warn_saturate+0xb5/0x170 ? refcount_warn_saturate+0xb5/0x170 nfs3svc_release_getacl+0xc9/0xe0 svc_process_common+0x5db/0xb60 ? __pfx_svc_process_common+0x10/0x10 ? __rcu_read_unlock+0x69/0xa0 ? __pfx_nfsd_dispatch+0x10/0x10 ? svc_xprt_received+0xa1/0x120 ? xdr_init_decode+0x11d/0x190 svc_process+0x2a7/0x330 svc_handle_xprt+0x69d/0x940 svc_recv+0x180/0x2d0 nfsd+0x168/0x200 ? __pfx_nfsd+0x10/0x10 kthread+0x1a2/0x1e0 ? kthread+0xf4/0x1e0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x60 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Kernel panic - not syncing: kernel: panic_on_warn set ... Clear acl_access/acl_default after posix_acl_release is called to prevent UAF from being triggered.

CVSS Details

Base Score
7.8
Exploitability
1.8
Impact
5.9
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability High

Threat Intelligence

EPSS Exploit Probability
12.7% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-416 Use After Free Memory Safety

Affected Products 8

VendorProductVersionRange
linuxlinux_kernel*≥2.6.13  –  <5.10.235
linuxlinux_kernel*≥5.11  –  <5.15.179
linuxlinux_kernel*≥5.16  –  <6.1.129
linuxlinux_kernel*≥6.2  –  <6.6.79
linuxlinux_kernel*≥6.7  –  <6.12.16
linuxlinux_kernel*≥6.13  –  <6.13.4
linuxlinux_kernel6.14any
linuxlinux_kernel6.14any

References 11

  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-082556.html
  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-265688.html
  • git.kernel.org https://git.kernel.org/stable/c/1fd94884174bd20beb1773990fd3b1aa877688d9
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/2e59b2b68782519560b3d6a41dd66a3d01a01cd3
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/55d947315fb5f67a35e4e1d3e01bb886b9c6decf
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/6f7cfee1a316891890c505563aa54f3476db52fd
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7faf14a7b0366f153284db0ad3347c457ea70136
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/8a1737ae42c928384ab6447f6ee1a882510e85fa
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/f8d871523142f7895f250a856f8c4a4181614510
    Patch
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/1fd94884174bd20beb1773990fd3b1aa877688d9
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/2e59b2b68782519560b3d6a41dd66a3d01a01cd3
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/55d947315fb5f67a35e4e1d3e01bb886b9c6decf
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/6f7cfee1a316891890c505563aa54f3476db52fd
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7faf14a7b0366f153284db0ad3347c457ea70136
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/8a1737ae42c928384ab6447f6ee1a882510e85fa
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/f8d871523142f7895f250a856f8c4a4181614510
    Patch