CVE-2026-77159 Red Hat CVE debrief

Who should care

Defenders responsible for libvirt installations, especially in environments where local attackers may have access to the swtpm account, should assess exposure and prioritize patching.

Why it matters

A local attacker can exploit a symlink-following flaw in libvirt's qemuTPMEmulatorPrepareHost() function to transfer ownership of an arbitrary file to the swtpm user, potentially leading to local privilege escalation and data tampering.

• Local privilege escalation to transfer ownership of arbitrary files
• Potential data tampering or unauthorized access to sensitive files

Technical summary

The qemuTPMEmulatorPrepareHost() function in libvirt uses a path-based chown() on the swtpm logfile without checking for symbolic links. A local attacker with access to the swtpm account can replace the logfile with a symlink, causing libvirtd (running as root) to transfer ownership of an arbitrary file to the swtpm user. This vulnerability is due to a lack of proper handling of symbolic links in the qemuTPMEmulatorPrepareHost() function, which allows a local attacker to potentially escalate privileges and tamper with data. The function does not adequately validate the swtpm logfile path, making it vulnerable to symlink attacks.

Defensive priority

Defenders should prioritize verifying and patching vulnerable libvirt installations, especially in environments where local attackers may have access to the swtpm account.

Recommended defensive actions

• Verify libvirt installations for vulnerability and apply patches
• Restrict access to the swtpm account
• Monitor for suspicious activity related to libvirt and swtpm
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the symlink-following flaw in libvirt's qemuTPMEmulatorPrepareHost() function. However, the corpus does not establish versions, exploitation, impact, or remediation, requiring verification from the supplied official sources.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.