CVE-2026-63809

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-07-19. a secondary CVSS source baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
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:

bpf: use kvfree() for replaced sysctl write buffer

proc_sys_call_handler() allocates its temporary sysctl buffer with kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since kvzalloc() may fall back to vmalloc() for large allocations, freeing that buffer with kfree() is wrong and can corrupt memory.

Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc allocations.

The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. Manual inspection confirms that the bug is still present in v7.1-rc5.

Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the test tree also included the accompanying fix for the stale ret == 1 check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines failslab injections to the proc_sys_call_handler() range, uses stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to /proc/sys/kernel/domainname from a task in the target cgroup. Under that setup, fail-nth=1 triggered the fault:

BUG: unable to handle page fault for address: ffffeb0200024d48 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 SMP KASAN NOPTI CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:kfree+0x6e/0x510 ... Call Trace: ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30 __cgroup_bpf_run_filter_sysctl+0x74d/0xc30 ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? __kvmalloc_node_noprof+0x345/0x870 ? proc_sys_call_handler+0x250/0x480 ? srso_return_thunk+0x5/0x5f proc_sys_call_handler+0x3a2/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? selinux_file_permission+0x39f/0x500 ? srso_return_thunk+0x5/0x5f ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ...

With this fix applied on top of the same test setup, rerunning the reproducer with fail-nth=1 yields no corresponding Oops reports.

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
5%
KEV
Not listed

Published

July 19, 2026

Last Modified

August 17, 2026

Advisory Details (8)

Auto-updated Jul 21, 2026
No patch confirmed yet.
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4
generic

bpf: use kvfree() for replaced sysctl write buffer - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004

Vendor Advisories for CVE-2026-63809(2)

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

Affected Packages

(5 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFixed inDependents
linux5.10.103-1 ... 5.10.92-2 (55 versions)5.10.262-1—
linux-6.16.1.106-3~deb11u1 ... 6.1.176-1~deb11u1 (21 versions)6.1.177-1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
linux6.1.106-1 ... 6.1.99-1 (54 versions)6.1.177-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
linux6.12.38-1 ... 6.12.95-1~bpo12+1 (29 versions)6.12.95-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
linux6.12.100-1 ... 7.1~rc7-1~exp1 (153 versions)7.1.3-1—

Data Freshness Timeline

(refreshed 32× in last 7d / 139× 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 184 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-63809?
CVE-2026-63809 is a high vulnerability published on July 19, 2026. In the Linux kernel, the following vulnerability has been resolved: bpf: use kvfree() for replaced sysctl write buffer procsyscall_handler() allocates its temporary sysctl buffer with kvzalloc() and passes it to cgroupbpfrunfiltersysctl(). Since kvzalloc() may fall back to vmalloc() for large…
When was CVE-2026-63809 disclosed?
CVE-2026-63809 was first published in the National Vulnerability Database on July 19, 2026, with the most recent update on August 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63809 actively exploited?
CVE-2026-63809 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 95.1% of all scored CVEs.
What is the CVSS score of CVE-2026-63809?
CVE-2026-63809 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-63809?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63809, 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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