CVE-2026-23557

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.

CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.02%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-617 CWE-617

Affected Products

Vendor	Product	Versions
xen	xen	>= 4.2.0

References

Advisories & Patches

https://xenbits.xenproject.org/xsa/advisory-484.html http://www.openwall.com/lists/oss-security/2026/04/28/11 http://xenbits.xen.org/xsa/advisory-484.html

Frequently Asked Questions

What is CVE-2026-23557? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-23557? +

CVE-2026-23557 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-23557? +

CVE-2026-23557 affects products from xen, specifically: xen. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-23557? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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