🛡️ CVE-2026-23557 on Debian — xen

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering. In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.

Distribution advisory

This page covers CVE-2026-23557 as tracked by Debian, for the package xen. The fix is available in version 4.20.3+127-gc42374a105-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

DEBIAN-CVE-2026-23557 is classified as CWE-617: Reachable Assertion. The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

Affected software

DEBIAN-CVE-2026-23557 is recorded against 1 package.

  • xen (fixed in 4.20.3+127-gc42374a105-1)

Timeline and source

Published on 19 May 2026 and last revised on 9 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2026-23557 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-05-19
Updated 2026-08-20
Modified 2026-08-09
Fix URL N/A

Affected Packages

Software From version Fixed in
xen — 4.20.3+127-gc42374a105-1

Vulnerability Monitoring

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