CVE-2025-21796

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2025-02-27. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 0

A fix is available — apply it.

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: ? 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 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 v3
7.8
EG Score
7.8(medium)
EG Risk
—
EPSS
13.6%
KEV
Not listed

Published

February 27, 2025

Last Modified

July 14, 2026

Advisory Details (10)

Auto-updated May 12, 2026
⚠️ Active exploitation confirmed. Patch available.
generic🔴 Active Exploitation

SSA-082556

https://cert-portal.siemens.com/productcert/html/ssa-082556.html
generic Patch Available

[SECURITY] [DLA 4178-1] linux security update

https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
generic Patch Available

[SECURITY] [DLA 4102-1] linux-6.1 security update

https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f8d871523142f7895f250a856f8c4a4181614510
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/8a1737ae42c928384ab6447f6ee1a882510e85fa
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7faf14a7b0366f153284db0ad3347c457ea70136
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/6f7cfee1a316891890c505563aa54f3476db52fd
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/55d947315fb5f67a35e4e1d3e01bb886b9c6decf
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/2e59b2b68782519560b3d6a41dd66a3d01a01cd3
generic

nfsd: clear acl_access/acl_default after releasing them - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/1fd94884174bd20beb1773990fd3b1aa877688d9

Vendor Advisories for CVE-2025-21796(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(31)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-virtual-hwe-20.04-edge (5.15.0.140.135) @ jammy2026-05-21ubuntu
ubuntulinux-tools-gcp-lts-22.04 (5.15.0.1083.79) @ jammy2026-05-21ubuntu
ubuntulinux-tools-gcp-fips (5.15.0.1083.73) @ jammy2026-05-21ubuntu
ubuntulinux-virtual-hwe-24.04-edge (6.11.0-26.26) @ oracular2026-05-21ubuntu
ubuntulinux-tools-azure-edge (5.15.0.1089.98~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-realtime (5.15.0.1084.88) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-fips (5.15.0.1089.74) @ jammy2026-05-21ubuntu
ubuntulinux-tools-aws-fips (5.15.0.1084.80) @ jammy2026-05-21ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1078.76) @ jammy2026-05-21ubuntu
ubuntulinux-virtual-hwe-20.04-edge (5.15.0.142.152~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-lowlatency-hwe-24.04-edge (6.11.0-1014.15~24.04.1) @ noble2026-05-21ubuntu
ubuntulinux-xilinx-zynqmp-tools-host (5.15.0-1050.54) @ jammy2026-05-21ubuntu
ubuntulinux-tools-gke-5.15 (5.15.0.1081.80) @ jammy2026-05-21ubuntu
ubuntulinux-tools-aws-edge (5.15.0.1084.91~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-aws (6.11.0-1014.15) @ oracular2026-05-21ubuntu
ubuntulinux-tools-oracle-lts-24.04 (6.8.0-1032.33) @ noble2026-05-21ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2028.29) @ noble2026-05-21ubuntu
ubuntulinux-virtual-6.8 (6.8.0-78.78) @ noble2026-05-21ubuntu
ubuntulinux-tools-ibm-lts-24.04 (6.8.0-1033.33) @ noble2026-05-21ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1035.39) @ noble2026-05-21ubuntu
ubuntulinux-tools-azure-nvidia-lts-24.04 (6.8.0-1022.23) @ noble2026-05-21ubuntu
ubuntulinux-xilinx-zynqmp-tools-5.4.0-1069 (5.4.0-1069.73) @ focal2026-05-21ubuntu
ubuntulinux-virtual-hwe-16.04-edge (4.15.0.242.254~16.04.1) @ xenial2026-05-21ubuntu
ubuntulinux-tools-gcp-fips-4.15 (4.15.0.2086.84) @ bionic2026-05-21ubuntu
ubuntulinux-tools-oracle-edge (5.4.0.1149.159~18.04.1) @ bionic2026-05-21ubuntu
ubuntulinux-tools-fips (4.4.0.1119.120) @ xenial2026-05-21ubuntu
ubuntulinux-tools-gcp-fips-5.4 (5.4.0.1154.96) @ focal2026-05-21ubuntu
ubuntulinux-tools-azure-lts-20.04 (5.4.0.1154.148) @ focal2026-05-21ubuntu
redhatkernel-0:5.14.0-611.5.1.el9_72025-11-11redhat
redhatkernel-0:6.12.0-124.8.1.el10_12025-11-11redhat
linuxKernel @ 5.10.235—osv

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(22)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 44× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 124 total refreshes for this CVE.

  1. 2026-07-22 14:07 UTCEPSS rescore
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  20. 2026-07-10 17:41 UTCOSV refresh
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  22. 2026-06-22 01:37 UTCOSV refresh
  23. 2026-06-21 14:56 UTCEPSS rescore
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  54. 2026-06-02 20:12 UTCEPSS rescore
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Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2025-21796?
CVE-2025-21796 is a high vulnerability published on February 27, 2025. In the Linux kernel, the following vulnerability has been resolved: nfsd: clear aclaccess/acldefault after releasing them If getting acldefault fails, aclaccess and acl_default will be released simultaneously. However, acl_access will still retain a pointer pointing to the released posix_acl, which…
When was CVE-2025-21796 disclosed?
CVE-2025-21796 was first published in the National Vulnerability Database on February 27, 2025, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-21796 actively exploited?
CVE-2025-21796 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-21796?
CVE-2025-21796 has a CVSS v3.1 base score of 7.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2025-21796?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-21796, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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