{"id":"CVE-2026-43331","state":"PUBLISHED","title":"x86/kexec: Disable KCOV instrumentation after load_segments()","description":"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's 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. ]","publishedAt":"2026-05-08T13:31:18.787Z","updatedAt":"2026-06-19T11:58:29.321Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"0e96cd314c0d819c1635d68125a4d77852c2162e","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"593d67032544b9271094fc9b43e437e017cb2b2f","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"1e3e98596c2769721ade0418434852fb3af4849a","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"de05c66fab8847237a9ca216934e56d3ee837f08","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"917e3ad3321e75ca0223d5ccf26ceda116aa51e1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kernel/Makefile","arch/x86/mm/Makefile"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kernel/Makefile","arch/x86/mm/Makefile"]}],"references":["https://git.kernel.org/stable/c/0e96cd314c0d819c1635d68125a4d77852c2162e","https://git.kernel.org/stable/c/593d67032544b9271094fc9b43e437e017cb2b2f","https://git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a","https://git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08","https://git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43331.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43331","state":"PUBLISHED","datePublished":"2026-05-08T13:31:18.787Z","dateUpdated":"2026-06-19T11:58:29.321Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.002Z"},"containers":{"cna":{"title":"x86/kexec: Disable KCOV instrumentation after load_segments()","descriptions":[{"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's 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. ]"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"0e96cd314c0d819c1635d68125a4d77852c2162e","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"593d67032544b9271094fc9b43e437e017cb2b2f","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"1e3e98596c2769721ade0418434852fb3af4849a","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"de05c66fab8847237a9ca216934e56d3ee837f08","versionType":"git"},{"version":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef","status":"affected","lessThan":"917e3ad3321e75ca0223d5ccf26ceda116aa51e1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kernel/Makefile","arch/x86/mm/Makefile"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kernel/Makefile","arch/x86/mm/Makefile"]}],"references":[{"url":"https://git.kernel.org/stable/c/0e96cd314c0d819c1635d68125a4d77852c2162e"},{"url":"https://git.kernel.org/stable/c/593d67032544b9271094fc9b43e437e017cb2b2f"},{"url":"https://git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a"},{"url":"https://git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08"},{"url":"https://git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-06-19T11:58:29.321Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.18.22"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.19.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}