How severe is CVE-2026-23557?

CVE-2026-23557 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-23557 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23557?

CVE-2026-23557 affects Xen. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23557?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-23557 have an EU (EUVD) identifier?

Yes. CVE-2026-23557 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30925.

When was CVE-2026-23557 published?

CVE-2026-23557 was published on 2026-05-19 and last updated on 2026-06-17.

CVE-2026-23557

CVE-2026-23557 is a medium-severity vulnerability in Xen with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-617.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (5th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30925
Weakness: CWE-617
Affected product: Xen
Published: 2026-05-19
Last modified: 2026-06-17

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.

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.
How severe is CVE-2026-23557?: CVE-2026-23557 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-23557 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23557?: CVE-2026-23557 affects Xen. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23557?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-23557 have an EU (EUVD) identifier?: Yes. CVE-2026-23557 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30925.
When was CVE-2026-23557 published?: CVE-2026-23557 was published on 2026-05-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:xen:xen:*:*:*:*:*:*:*:*

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