Remote kernel crash via non-atomic GCOV counters
Published Jul 19, 2026 · Updated Jul 19, 2026
Out-of-bounds writes in Linux Kernel before 6.18.38 or 7.1.3 allow remote attackers to crash systems via parallel IPComp traffic. In inflate_fast(), GCC-generated loops reload a shared non-atomic GCOV counter for the base address, start index, and end bound, so another CPU can change the values between loads and drive writes beyond the decompression buffer. Reachability requires a GCOV-instrumented multicore kernel, a matching IPComp security association, and concurrent packet processing; the demonstrated consequence is a kernel page fault and system crash.
Summary
What happened
Out-of-bounds writes in Linux Kernel before 6.18.38 or 7.1.3 allow remote attackers to crash systems via parallel IPComp traffic. In inflate_fast(), GCC-generated loops reload a shared non-atomic GCOV counter for the base address, start index, and end bound, so another CPU can change the values between loads and drive writes beyond the decompression buffer. Reachability requires a GCOV-instrumented multicore kernel, a matching IPComp security association, and concurrent packet processing; the demonstrated consequence is a kernel page fault and system crash.
The record
- CVE
- CVE-2026-63825
- Published
- Jul 19, 2026
- Updated
- Jul 19, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-787, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 19, 2026CVE publishedPublication date reported by the CVE source.
- Jul 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <6.18.38
- Affected versionversion=0 <7.1.3
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <49d893b9cbcfc5802a32e53a64c6c6956670d65b
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <56cb9b7d96b28a1173a510ab25354b6599ad3a33
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5b959c1dbb4522b9e3ac4e26ad638b8784869841
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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