# CVE-2026-43331: x86/kexec: Disable KCOV instrumentation after load_segments() CVE-2026-43331 is fixed in 14 products on 1 platform, first by DEBIAN-CVE-2026-43331, released May 15, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-43331 - Priority: Routine - CVSS: 5.5 (Moderate) - EPSS: 0.0012 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: May 8, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43331 ## Description 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. ] ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | dtb-aarch64 opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-64kb opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-64kb sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-azure opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-azure sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-default opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-default sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-default-base opensuse-leap 16.0 | 6.12.0-160000.38.1.160000.2.22 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-default-base sles 16.0 | 6.12.0-160000.38.1.160000.2.23 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-docs opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-docs sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-kvmsmall opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-kvmsmall sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-obs-build opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-obs-qa opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-obs-qa sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-rt opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-source opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-source sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-syms opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-syms sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | kernel-zfcpdump opensuse-leap 16.0 | 6.12.0-160000.38.1 | [OPENSUSE-SU-2026:21910-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21910-1.md) | Sep 22, 2026 | | Linux | kernel-zfcpdump sles 16.0 | 6.12.0-160000.38.1 | [SUSE-SU-2026:23902-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23902-1.md) | Sep 22, 2026 | | Linux | linux Debian 13.5 (trixie) | 6.12.94-1 | [DEBIAN-CVE-2026-43331](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43331.md) | May 15, 2026 | | Linux | linux Debian 14 | 6.19.12-1 | [DEBIAN-CVE-2026-43331](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43331.md) | May 15, 2026 | --- Data as of 2026-11-08T06:59:42Z UTC. 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