Skip to main content
VulnerabilityPublished Updated

CVE-2026-63825: Linux kernel · gcov: use atomic counter updates to fix concurrent access crashes

Affects Linux kernelSource GCVE Database

0
Authoritative record:CVE-2026-63825· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical · fixed in 7.0.0-1012.12~24.04.1 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 7.0.0-1012.12~24.04.1, 7.0.0-1014.14~24.04.1, 7.0.0-1011.11~24.04.1 +14
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-31.31
Fixed in
  • 7.0.0-31.31
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1012.12
Fixed in
  • 7.0.0-1012.12
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1014.14
Fixed in
  • 7.0.0-1014.14
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threatsAffected
  • 7.0.0-1003.3 – 7.0.0-1016.16
9 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1011.11
Fixed in
  • 7.0.0-1011.11
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1006.7
Fixed in
  • 7.0.0-1006.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available and should be applied by updating to the fixed Linux kernel versions. The fix involves enabling atomic updates for GCOV counters using the -fprofile-update=prefer-atomic compiler flag, which prevents concurrent access crashes. The patch is included in recent Linux kernel releases and distributions such as Ubuntu have issued security notices with updated kernel packages. Users should upgrade to the patched kernel versions as soon as possible to mitigate this vulnerability.

Description

A concurrency issue in the Linux kernel's GCOV instrumentation caused out-of-bounds memory writes during concurrent execution on multiple CPUs. This was due to non-atomic updates of global GCOV counters used in optimized loops, leading to inconsistent values and memory corruption. The flaw was fixed by enabling atomic counter updates via a compiler flag, preventing the compiler from merging counters with loop induction variables. This vulnerability has a critical severity with a CVSS score of 9.8 and affects multiple Linux kernel versions prior to 7.0.0-31.31 and several specific older versions. A patch is available and included in recent Linux kernel updates.

References

Community reviews

Loading reviews…