Vulnerability-Lookup

FKIE_CVE-2026-43331

Vulnerability from fkie_nvd - Published: 2026-05-08 14:16 - Updated: 2026-05-18 12:39

Severity

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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. ]

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0

JSON

To clipboard

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      "lang": "en",
      "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. ]"
    }
  ],
  "id": "CVE-2026-43331",
  "lastModified": "2026-05-18T12:39:01.053",
  "metrics": {
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          "attackVector": "LOCAL",
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          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
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  },
  "published": "2026-05-08T14:16:42.763",
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}

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

Vulnerability from cvelistv5 – Published: 2026-05-08 13:31 – Updated: 2026-05-11 22:22

Title

x86/kexec: Disable KCOV instrumentation after load_segments()

Summary

Severity

No CVSS data available.

Assigner

Linux

References

3 references

URL	Tags
https://git.kernel.org/stable/c/1e3e98596c2769721…
https://git.kernel.org/stable/c/de05c66fab8847237…
https://git.kernel.org/stable/c/917e3ad3321e75ca0…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 1e3e98596c2769721ade0418434852fb3af4849a (git) Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < de05c66fab8847237a9ca216934e56d3ee837f08 (git) Affected: 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef , < 917e3ad3321e75ca0223d5ccf26ceda116aa51e1 (git)
Linux	Linux	Affected: 6.6 Unaffected: 0 , < 6.6 (semver) Unaffected: 6.18.22 , ≤ 6.18.* (semver) Unaffected: 6.19.12 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date	Other

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.

Action not permitted

FKIE_CVE-2026-43331

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

Tags

Sightings

Nomenclature