CVE-2026-23557
Analyzed Analyzed - Analysis Complete
Xenstored Assertion Failure in Transaction Handling

Publication date: 2026-05-19

Last updated on: 2026-05-19

Assigner: Xen Project

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.
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Meta Information
Published
2026-05-19
Last Modified
2026-05-19
Generated
2026-06-10
AI Q&A
2026-05-19
EPSS Evaluated
2026-06-08
NVD
CVE-2026-23557
EUVD
EUVD-2026-30925
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
xen xen From 4.2.0 (inc)
Helpful Resources
Exploitability
CWE
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KEV
KEV Icon
CWE ID Description
CWE-617 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.
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Executive Summary

CVE-2026-23557 is a vulnerability in Xen's xenstored service where any guest can cause the service to crash by issuing an XS_RESET_WATCHES command within a transaction.

The crash happens because an assert() statement is triggered, which causes xenstored to terminate unexpectedly.

This vulnerability affects systems where xenstored is built without the NDEBUG macro defined, which is the default for most Xen releases.

Systems using the OCaml variant (oxenstored) or the C variant built with NDEBUG defined are not vulnerable.

The issue impacts all Xen systems from version 4.2 onwards, while versions prior to 4.1 are unaffected.

Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

Detection Guidance

There is no specific detection method or commands provided in the available resources to identify exploitation of this vulnerability on your network or system.

The vulnerability involves any unprivileged guest domain sending an XS_RESET_WATCHES command within a transaction to xenstored, causing it to crash due to an assert() failure. Monitoring for unexpected crashes or restarts of the xenstored service could be an indirect indicator.

Since no explicit detection commands or network signatures are documented, the best approach is to ensure your Xen system is patched to the fixed versions.

Impact Analysis

This vulnerability can cause a denial of service (DoS) by crashing the xenstored service.

When xenstored crashes, further Xenstore operations become impossible, which affects domain administration and management.

This means that any guest can disrupt the normal operation of the Xen environment by triggering this crash.

There is no known mitigation other than applying patches that fix the issue.

Mitigation Strategies

There is no known mitigation to prevent this vulnerability from being exploited without applying patches.

The recommended immediate step is to apply the available patches for the affected Xen versions to resolve the issue.

Note that the vulnerability only affects xenstored built without NDEBUG defined, which is the default for most Xen releases.

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