CVE-2026-77159: libvirt UNIX Symbolic Link (Symlink) Following
Vulnerability summary
CVE-2026-77159 is a medium (CVSS 5.5) UNIX Symbolic Link (Symlink) Following vulnerability in libvirt. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 5% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 13 · Related 13Timeline
- 11-09-2026PublishedVulnerability first disclosed.
- 15-09-2026Last modifiedVulnerability information updated.
Description
A symlink-following flaw was found in libvirt's qemuTPMEmulatorPrepareHost() function. The function 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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- NVDNIST5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
0.16%
Chance of exploitation in the next 30 days
Percentile
5%
Versus all other CVEs
30-day change
0.00 pp
From 0.16% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu2 products
- libvirtAll versions (No fix recorded) | < 8.0.0-1ubuntu7.21 | < 10.0.0-2ubuntu8.19 | < 12.0.0-1ubuntu5.5
- libvirt-hwe< 12.0.0-1ubuntu5.5
Debian1 product
- libvirtAll versions (No fix recorded) | < 12.7.0-1
2 vendors · 3 products
