CVE-2025-21796

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.6%, top 52% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: cna:linux, epss, ghsa
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 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
9.8
EG Score
9.8(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
49%
KEV
Not listed

Published

February 27, 2025

Last Modified

September 8, 2026

Advisory Details (10)

Auto-updated Sep 15, 2026
No patch confirmed yet.
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/1fd94884174bd20beb1773990fd3b1aa877688d9
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/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/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/8a1737ae42c928384ab6447f6ee1a882510e85fa
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

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-tools-gcp-lts-22.04 (5.15.0.1083.79) @ jammy2026-07-30ubuntu
ubuntulinux-tools-gcp-fips (5.15.0.1083.73) @ jammy2026-07-30ubuntu
ubuntulinux-tools-nvidia-tegra-rt (5.15.0.1037.37) @ jammy2026-07-30ubuntu
ubuntulinux-tools-realtime (5.15.0.1084.88) @ jammy2026-07-30ubuntu
ubuntulinux-tools-aws-fips (5.15.0.1084.80) @ jammy2026-07-30ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1078.76) @ jammy2026-07-30ubuntu
ubuntulinux-virtual-hwe-20.04-edge (5.15.0.142.152~20.04.1) @ focal2026-07-30ubuntu
ubuntulinux-tools-lowlatency-hwe-24.04-edge (6.11.0-1014.15~24.04.1) @ noble2026-07-30ubuntu
ubuntulinux-xilinx-zynqmp-tools-host (5.15.0-1050.54) @ jammy2026-07-30ubuntu
ubuntulinux-tools-aws-edge (5.15.0.1084.91~20.04.1) @ focal2026-07-30ubuntu
ubuntulinux-tools-aws (6.11.0-1014.15) @ oracular2026-07-30ubuntu
ubuntulinux-tools-oracle-lts-24.04 (6.8.0-1032.33) @ noble2026-07-30ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2028.29) @ noble2026-07-30ubuntu
ubuntulinux-tools-lowlatency-hwe-22.04-edge (6.8.0-78.78.1~22.04.1) @ jammy2026-07-30ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1035.39) @ noble2026-07-30ubuntu
ubuntulinux-tools-oracle-edge (5.4.0.1149.159~18.04.1) @ bionic2026-07-30ubuntu
ubuntulinux-tools-fips (4.4.0.1119.120) @ xenial2026-07-30ubuntu
ubuntulinux-tools-gcp-fips-5.4 (5.4.0.1154.96) @ focal2026-07-30ubuntu
ubuntulinux-tools-azure-lts-20.04 (5.4.0.1154.148) @ focal2026-07-30ubuntu
ubuntulinux-tools-azure (4.15.0.1193.208~14.04.1) @ trusty2026-07-30ubuntu
ubuntulinux-tools-azure-fips-5.4 (5.4.0.1155.92) @ focal2026-07-30ubuntu
ubuntulinux-tools-raspi-hwe-18.04-edge (5.4.0.1134.147~18.04.1) @ bionic2026-07-30ubuntu
ubuntulinux-tools-aws-fips-5.4 (5.4.0.1151.98) @ focal2026-07-30ubuntu
ubuntulinux-virtual-lts-xenial (4.4.0.273.307~14.04.1) @ trusty2026-07-30ubuntu
ubuntulinux-tools-oracle-lts-20.04 (5.4.0.1149.143) @ focal2026-07-30ubuntu
ubuntulinux-tools-aws (4.4.0.1186.190) @ xenial2026-07-30ubuntu
ubuntulinux-tools-kvm (4.15.0.1168.159) @ bionic2026-07-30ubuntu
ubuntulinux-tools-azure-fips-4.15 (4.15.0.2102.98) @ bionic2026-07-30ubuntu
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.

Affected Packages

(5 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFixed inDependents
linux5.10.103-1 ... 5.10.92-2 (45 versions)5.10.237-1—
linux-6.16.1.106-3~deb11u1 ... 6.1.128-1~deb11u1 (6 versions)6.1.129-1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 6.1.99-1 (35 versions)6.1.129-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux—6.12.16-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux—6.12.16-1—

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 6× in last 7d / 31× 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 193 total refreshes for this CVE.

  1. 2026-09-18 19:27 UTCEPSS rescore
  2. 2026-09-16 14:06 UTCEPSS rescore
  3. 2026-09-16 05:13 UTCEPSS rescore
  4. 2026-09-15 03:09 UTCEPSS rescore
  5. 2026-09-13 16:46 UTCEPSS rescore
  6. 2026-09-12 15:00 UTCEPSS rescore
  7. 2026-09-11 14:51 UTCEPSS rescore
  8. 2026-09-11 09:35 UTCEPSS rescore
  9. 2026-09-10 09:33 UTCEPSS rescore
  10. 2026-09-08 21:59 UTCEPSS rescore
  11. 2026-09-08 09:51 UTCEG score recompute
  12. 2026-09-08 09:51 UTCVendor advisory
  13. 2026-09-08 09:51 UTCGHSA enrichment
  14. 2026-09-07 16:00 UTCEPSS rescore
  15. 2026-09-07 12:48 UTCOSV refresh
  16. 2026-09-06 13:46 UTCEPSS rescore
  17. 2026-09-06 13:46 UTCEPSS rescore
  18. 2026-09-05 15:28 UTCEPSS rescore
  19. 2026-09-04 05:05 UTCEPSS rescore
  20. 2026-09-02 14:11 UTCEPSS rescore
  21. 2026-09-01 13:52 UTCEPSS rescore
  22. 2026-09-01 04:38 UTCEPSS rescore
  23. 2026-08-30 19:16 UTCEPSS rescore
  24. 2026-08-30 01:21 UTCEPSS rescore
  25. 2026-08-28 21:40 UTCEPSS rescore
Show 75 more
  1. 2026-08-27 14:24 UTCEPSS rescore
  2. 2026-08-25 13:47 UTCEPSS rescore
  3. 2026-08-23 00:18 UTCEPSS rescore
  4. 2026-08-21 23:48 UTCEPSS rescore
  5. 2026-08-20 22:54 UTCEPSS rescore
  6. 2026-08-20 22:31 UTCOSV refresh
  7. 2026-08-19 17:03 UTCEPSS rescore
  8. 2026-08-18 13:47 UTCEPSS rescore
  9. 2026-08-17 13:46 UTCEPSS rescore
  10. 2026-08-16 14:55 UTCEPSS rescore
  11. 2026-08-16 02:13 UTCEPSS rescore
  12. 2026-08-16 02:13 UTCEPSS rescore
  13. 2026-08-15 01:29 UTCEPSS rescore
  14. 2026-08-13 21:59 UTCEPSS rescore
  15. 2026-08-12 13:50 UTCEPSS rescore
  16. 2026-08-10 23:59 UTCEPSS rescore
  17. 2026-08-09 13:45 UTCEPSS rescore
  18. 2026-08-07 16:26 UTCEPSS rescore
  19. 2026-08-06 13:46 UTCEPSS rescore
  20. 2026-08-05 19:16 UTCEPSS rescore
  21. 2026-08-05 14:02 UTCEG score recompute▲ 2.00
  22. 2026-08-05 14:02 UTCVendor advisory
  23. 2026-08-05 14:02 UTCGHSA enrichment
  24. 2026-08-05 12:31 UTCMITRE cvelistV5CVSS v3 → 9.8 · severity → CRITICAL
  25. 2026-08-04 15:09 UTCEPSS rescore
  26. 2026-08-04 10:37 UTCEPSS rescore
  27. 2026-08-03 10:35 UTCEPSS rescore
  28. 2026-08-02 02:25 UTCEPSS rescore
  29. 2026-08-01 04:15 UTCEPSS rescore
  30. 2026-07-30 16:27 UTCEPSS rescore
  31. 2026-07-30 07:19 UTCEG score recompute
  32. 2026-07-30 07:19 UTCVendor advisory
  33. 2026-07-30 07:19 UTCGHSA enrichment
  34. 2026-07-30 06:24 UTCNVD updateCVSS v3 → 7.8 · severity → HIGH
  35. 2026-07-30 06:18 UTCMITRE cvelistV5CVSS v3 → 9.8 · severity → CRITICAL
  36. 2026-07-30 01:29 UTCEPSS rescore
  37. 2026-07-28 15:35 UTCEPSS rescore
  38. 2026-07-28 01:24 UTCOSV refresh
  39. 2026-07-27 14:12 UTCEPSS rescore
  40. 2026-07-26 14:53 UTCEPSS rescore
  41. 2026-07-25 14:17 UTCEPSS rescore
  42. 2026-07-24 14:17 UTCEPSS rescore
  43. 2026-07-23 14:17 UTCEPSS rescore
  44. 2026-07-23 02:50 UTCEG score recompute
  45. 2026-07-22 14:07 UTCEPSS rescore
  46. 2026-07-22 14:07 UTCEPSS rescore
  47. 2026-07-21 15:24 UTCEPSS rescore
  48. 2026-07-20 17:07 UTCEPSS rescore
  49. 2026-07-19 14:30 UTCEPSS rescore
  50. 2026-07-19 14:30 UTCEPSS rescore
  51. 2026-07-19 02:28 UTCEPSS rescore
  52. 2026-07-19 02:28 UTCEPSS rescore
  53. 2026-07-18 10:03 UTCEPSS rescore
  54. 2026-07-16 17:02 UTCEPSS rescore
  55. 2026-07-15 16:57 UTCEPSS rescore
  56. 2026-07-15 16:57 UTCEPSS rescore
  57. 2026-07-15 01:59 UTCEPSS rescore
  58. 2026-07-13 06:12 UTCEPSS rescore
  59. 2026-07-13 06:12 UTCEPSS rescore
  60. 2026-07-12 05:46 UTCEPSS rescore
  61. 2026-07-12 05:46 UTCEPSS rescore
  62. 2026-07-11 08:27 UTCEPSS rescore
  63. 2026-07-11 08:26 UTCEPSS rescore
  64. 2026-07-10 17:41 UTCOSV refresh
  65. 2026-07-09 19:09 UTCEPSS rescore
  66. 2026-07-08 15:14 UTCEPSS rescore
  67. 2026-07-07 13:45 UTCEPSS rescore
  68. 2026-07-06 16:26 UTCEPSS rescore
  69. 2026-07-06 02:22 UTCEPSS rescore
  70. 2026-07-06 02:22 UTCEPSS rescore
  71. 2026-07-05 02:30 UTCEPSS rescore
  72. 2026-07-04 06:30 UTCEPSS rescore
  73. 2026-07-01 15:06 UTCEPSS rescore
  74. 2026-06-30 23:21 UTCEPSS rescore
  75. 2026-06-30 23:21 UTCEPSS rescore

Frequently asked(5)

What is CVE-2025-21796?
CVE-2025-21796 is a critical 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 September 8, 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 1% probability of exploitation in the next 30 days, which ranks it in the top 51.0% of all scored CVEs.
What is the CVSS score of CVE-2025-21796?
CVE-2025-21796 has a CVSS v4.0 base score of 9.8 (CNA self-assessment; 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.

Dependency Blast Radius

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