CVE-2025-11931: Integer Underflow Leads to Out-of-Bounds Access in XChaCha20-Poly1305 Decrypt

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.3%

EPSS score, percentile 27.4 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

2.1 Low

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• before 5.8.4

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

Integer Underflow Leads to Out-of-Bounds Access in XChaCha20-Poly1305 Decrypt. This issue is hit specifically with a call to the function wc_XChaCha20Poly1305_Decrypt() which is not used with TLS connections, only from direct calls from an application.

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2025-11931 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 21 Nov 2025.
• The CVE record carries a CVSS v4.0 base score of 2.1 (Low), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.3% (percentile 27.4), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name AISLE as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

Integer Underflow Leads to Out-of-Bounds Access in XChaCha20-Poly1305 Decrypt

Integer Underflow Leads to Out-of-Bounds Access in XChaCha20-Poly1305 Decrypt. This issue is hit specifically with a call to the function wc_XChaCha20Poly1305_Decrypt() which is not used with TLS connections, only from direct calls from an application.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline