CVE-2026-31586

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-04-24. 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

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)
EPSS
2.8%
KEV
Not listed

Published

April 24, 2026

Last Modified

June 14, 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.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 41× 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 171 total refreshes for this CVE.

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

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 June 14, 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 2.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
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.

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