5.5

CVE-2026-79611: VMX: VMentry failure with branch tracing and blocked states

Awaiting analysis
AliasesALPINE-CVE-2026-79611DEBIAN-CVE-2026-79611UBUNTU-CVE-2026-79611
Published 13-10-2026Last modified 20-10-2026

Vulnerability summary

CVE-2026-79611 is a medium (CVSS 5.5) vulnerability in xen. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 5.2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.16%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 5 · Related 5
OPENSUSE-SU-2026:12138-1SUSE-SU-2026:4641-1SUSE-SU-2026:4642-1SUSE-SU-2026:4732-1SUSE-SU-2026:4942-1

Timeline

  1. 13-10-2026
    PublishedVulnerability first disclosed.
  2. 20-10-2026
    Last modifiedVulnerability information updated.

Description

For XSA-308 logic was introduced, as VMX VMEntry checks do not like the exact combination of state which occurs when #DB in intercepted, Single Stepping is active, and blocked by STI/MovSS is active, despite this being a legitimate state to be in. The resulting VMEntry failure is fatal to the guest. Sadly there is another special sub-case of the above, with branch tracing enabled. In that case the prior adjustment would still cause a VMentry failure, as before fatal to the guest.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.16%

Chance of exploitation in the next 30 days

Percentile

5%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

14-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • xen< 4.19.6-r2 | < 4.20.4-r2 | < 4.21.2-r2
Debian1 product
  • xenAll versions (No fix recorded) | < 4.20.4+39-gf1e1321c87-0+deb13u1 | < 4.20.4+39-gf1e1321c87-1
Ubuntu1 product
  • xenAll versions (No fix recorded)

3 vendors · 3 products

References

8 links