CVE-2026-15311: XSS (CVSS 3.5)

Description

A vulnerability was identified in NousResearch hermes-agent up to 2026.5.29.2. Affected by this issue is the function MatrixAdapter._markdown_to_html of the file gateway/platforms/matrix.py of the component Matrix Adapter. Such manipulation leads to cross site scripting. The attack can be executed remotely. The exploit is publicly available and might be used. The pull request to fix this issue awaits acceptance.

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CVSS v3.1 Score

3.5

LOW

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

EPSS — Exploit Prediction

0.0020

Probability of exploitation

0.10%

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-79 Cross-site Scripting (XSS)

CWE-94 CWE-94

References

Other References

https://github.com/NousResearch/hermes-agent/ https://github.com/NousResearch/hermes-agent/issues/42667 https://github.com/NousResearch/hermes-agent/pull/42759 https://vuldb.com/cve/CVE-2026-15311 https://vuldb.com/submit/852843 https://vuldb.com/vuln/377247 https://vuldb.com/vuln/377247/cti

Frequently Asked Questions

What is CVE-2026-15311? +

A vulnerability was identified in NousResearch hermes-agent up to 2026.5.29.2. Affected by this issue is the function MatrixAdapter._markdown_to_html of the file gateway/platforms/matrix.py of the component Matrix Adapter. Such manipulation leads to cross site scripting. The attack can be executed remotely. The exploit is publicly available and might be used. The pull request to fix this issue awaits acceptance. It has a CVSS v3.1 base score of 3.5 (LOW).

How severe is CVE-2026-15311? +

CVE-2026-15311 has a CVSS v3.1 score of 3.5 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0020, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-15311? +

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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