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CVE-2026-43331 (GCVE-0-2026-43331)

Vulnerability from cvelistv5 – Published: 2026-05-08 13:31 – Updated: 2026-06-19 11:58
VLAI
Title
x86/kexec: Disable KCOV instrumentation after load_segments()
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/kexec: Disable KCOV instrumentation after load_segments() The load_segments() function changes segment registers, invalidating GS base (which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any subsequent instrumented C code call (e.g. native_gdt_invalidate()) begins crashing the kernel in an endless loop. To reproduce the problem, it's sufficient to do kexec on a KCOV-instrumented kernel: $ kexec -l /boot/otherKernel $ kexec -e The real-world context for this problem is enabling crash dump collection in syzkaller. For this, the tool loads a panic kernel before fuzzing and then calls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC and CONFIG_KCOV to be enabled simultaneously. Adding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc()) is also undesirable as it would introduce an extra performance overhead. Disabling instrumentation for the individual functions would be too fragile, so disable KCOV instrumentation for the entire machine_kexec_64.c and physaddr.c. If coverage-guided fuzzing ever needs these components in the future, other approaches should be considered. The problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported there. [ bp: Space out comment for better readability. ]
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 0e96cd314c0d819c1635d68125a4d77852c2162e (git)
Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 593d67032544b9271094fc9b43e437e017cb2b2f (git)
Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 1e3e98596c2769721ade0418434852fb3af4849a (git)
Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < de05c66fab8847237a9ca216934e56d3ee837f08 (git)
Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 917e3ad3321e75ca0223d5ccf26ceda116aa51e1 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.6
Unaffected: 0 , < 6.6 (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/kexec: Disable KCOV instrumentation after load_segments()\n\nThe load_segments() function changes segment registers, invalidating GS base\n(which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any\nsubsequent instrumented C code call (e.g. native_gdt_invalidate()) begins\ncrashing the kernel in an endless loop.\n\nTo reproduce the problem, it\u0027s sufficient to do kexec on a KCOV-instrumented\nkernel:\n\n  $ kexec -l /boot/otherKernel\n  $ kexec -e\n\nThe real-world context for this problem is enabling crash dump collection in\nsyzkaller. For this, the tool loads a panic kernel before fuzzing and then\ncalls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC\nand CONFIG_KCOV to be enabled simultaneously.\n\nAdding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc())\nis also undesirable as it would introduce an extra performance overhead.\n\nDisabling instrumentation for the individual functions would be too fragile,\nso disable KCOV instrumentation for the entire machine_kexec_64.c and\nphysaddr.c. If coverage-guided fuzzing ever needs these components in the\nfuture, other approaches should be considered.\n\nThe problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported\nthere.\n\n  [ bp: Space out comment for better readability. ]"
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For this, the tool loads a panic kernel before fuzzing and then\\ncalls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC\\nand CONFIG_KCOV to be enabled simultaneously.\\n\\nAdding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc())\\nis also undesirable as it would introduce an extra performance overhead.\\n\\nDisabling instrumentation for the individual functions would be too fragile,\\nso disable KCOV instrumentation for the entire machine_kexec_64.c and\\nphysaddr.c. If coverage-guided fuzzing ever needs these components in the\\nfuture, other approaches should be considered.\\n\\nThe problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported\\nthere.\\n\\n  [ bp: Space out comment for better readability. 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      "cve": "CVE-2026-43331",
      "id": "CVE-2026-43331",
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      "title": "kernel: x86/kexec: Disable KCOV instrumentation after load_segments()",
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      "source": "SUSE CSAF VEX",
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      "title": "SUSE CVE CVE-2026-43331",
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}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.