CVE-2026-31586

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-04-24. the CNA's CVSS baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:linux, epss, ghsa
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn()

cgwb_release_workfn() calls css_put(wb->blkcg_css) and then later accesses wb->blkcg_css again via blkcg_unpin_online(). If css_put() drops the last reference, the blkcg can be freed asynchronously (css_free_rwork_fn -> blkcg_css_free -> kfree) before blkcg_unpin_online() dereferences the pointer to access blkcg->online_pin, resulting in a use-after-free:

BUG: KASAN: slab-use-after-free in blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367) Write of size 4 at addr ff11000117aa6160 by task kworker/71:1/531 Workqueue: cgwb_release cgwb_release_workfn Call Trace: blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367) cgwb_release_workfn (mm/backing-dev.c:629) process_scheduled_works (kernel/workqueue.c:3278 kernel/workqueue.c:3385)

Freed by task 1016: kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6246 mm/slub.c:6561) css_free_rwork_fn (kernel/cgroup/cgroup.c:5542) process_scheduled_works (kernel/workqueue.c:3302 kernel/workqueue.c:3385)

** Stack based on commit 66672af7a095 ("Add linux-next specific files for 20260410")

I am seeing this crash sporadically in Meta fleet across multiple kernel versions. A full reproducer is available at: https://github.com/leitao/debug/blob/main/reproducers/repro_blkcg_uaf.sh

(The race window is narrow. To make it easily reproducible, inject a msleep(100) between css_put() and blkcg_unpin_online() in cgwb_release_workfn(). With that delay and a KASAN-enabled kernel, the reproducer triggers the splat reliably in less than a second.)

Fix this by moving blkcg_unpin_online() before css_put(), so the cgwb's CSS reference keeps the blkcg alive while blkcg_unpin_online() accesses it.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity78% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

Published

April 24, 2026

Last Modified

August 5, 2026

Advisory Details (9)

Auto-updated Jun 3, 2026
No patch confirmed yet.
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/ea3af09eb87d8f8708c66747fcf1a2762902e839
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/dfc8292a1d6782c76b626315605e0585a5a18447
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/8f5857be99f1ed1fa80991c72449541f634626ee
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/740ba1ebb223f137ff088ab74d533a13f9167bd8
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/67cb119d32f35e32acd0393bbeb318b2bb1fdafe
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/50879a3c1faf06e661090015d59e2127255cff27
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/23acef4156c260e8598397a1a2e8b3a23e919893
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/1bd36e93b542d9dd020190c6607c6a3663405195
generic

mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/115a5266749dcde7fe4127e8623d19c752088f69

Vendor Advisories for CVE-2026-31586(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
linuxKernel @ 5.10.258—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 (54 versions)5.10.259-1—
linux-6.16.1.106-3~deb11u1 ... 6.1.174-1~deb11u1 (20 versions)6.1.176-1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 6.1.99-1 (53 versions)6.1.176-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux6.12.38-1 ... 6.12.85-1~bpo12+1 (17 versions)6.12.85-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 6.19~rc8-1~exp1 (126 versions)6.19.14-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(24)

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 8× in last 7d / 74× 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 263 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-31586?
CVE-2026-31586 is a high vulnerability published on April 24, 2026. In the Linux kernel, the following vulnerability has been resolved: mm: blk-cgroup: fix use-after-free in cgwbreleaseworkfn() cgwbreleaseworkfn() calls cssput(wb->blkcgcss) and then later accesses wb->blkcgcss again via blkcgunpinonline(). If cssput() drops the last reference, the blkcg can be…
When was CVE-2026-31586 disclosed?
CVE-2026-31586 was first published in the National Vulnerability Database on April 24, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-31586 actively exploited?
CVE-2026-31586 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 97.3% of all scored CVEs.
What is the CVSS score of CVE-2026-31586?
CVE-2026-31586 has a CVSS v4.0 base score of 7.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-31586?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-31586, 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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