What’s Vulnerable › Vulnerabilities

CVE-2021-43056

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-28 · updated 2026-06-17

Description

An issue was discovered in the Linux kernel for powerpc before 5.14.15. It allows a malicious KVM guest to crash the host, when the host is running on Power8, due to an arch/powerpc/kvm/book3s_hv_rmhandlers.S implementation bug in the handling of the SRR1 register values.

Affected products

• Fedoraproject Fedora: 33, 34, 35
• Linux kernel: from 5.2 before 5.4.15 — fixed in 5.4.15

How to fix

Upgrade to a fixed version: Linux kernel 5.4.15. Check the vendor advisory for mitigations.

References

• http://www.openwall.com/lists/oss-security/2021/10/28/1
• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.14.15
• https://git.kernel.org/linus/cdeb5d7d890e14f3b70e8087e745c4a6a7d9f337
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AA7EAPPKWG4LMTQQLNNSKATY6ST2KQFE/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBM4FP3IT3JZ2O7EBS7TEOG657N4ZGRE/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRAIS3PG4EV5WFLYESR6FXWM4BJJGWVA/
• https://lore.kernel.org/linuxppc-dev/87pmrtbbdt.fsf%40mpe.ellerman.id.au/T/#u
• http://www.openwall.com/lists/oss-security/2021/10/28/1
• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.14.15
• https://git.kernel.org/linus/cdeb5d7d890e14f3b70e8087e745c4a6a7d9f337
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AA7EAPPKWG4LMTQQLNNSKATY6ST2KQFE/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBM4FP3IT3JZ2O7EBS7TEOG657N4ZGRE/

Get alerted when CVE-2021-43056 or the next vulnerability affects your stack