CVE-2026-59220: open webui — Exploit & Fix

Description

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.2 before 0.10.0, the SKILL_MENTION_RE and strip_re regular expressions in backend/open_webui/utils/middleware.py parsed <$skillId|label> skill mentions with overlapping quantifiers, allowing an authenticated chat message containing <$ without a closing > to trigger quadratic backtracking and block the asyncio event loop. This issue is fixed in version 0.10.0.

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CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0032

Probability of exploitation

0.24%

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-1333 CWE-1333

Affected Products

Vendor	Product	Versions
openwebui	open_webui	0.9.2 — 0.10.0

References

Advisories & Patches

https://github.com/open-webui/open-webui/commit/61a26722155ec6ee1b629cf8dfcf975098c18331 https://github.com/open-webui/open-webui/security/advisories/GHSA-ffpj-xv5c-p3gw https://github.com/open-webui/open-webui/security/advisories/GHSA-ffpj-xv5c-p3gw

Exploits

https://github.com/open-webui/open-webui/security/advisories/GHSA-ffpj-xv5c-p3gw https://github.com/open-webui/open-webui/security/advisories/GHSA-ffpj-xv5c-p3gw

Other References

https://github.com/open-webui/open-webui/releases/tag/v0.10.0

Frequently Asked Questions

What is CVE-2026-59220? +

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.2 before 0.10.0, the SKILL_MENTION_RE and strip_re regular expressions in backend/open_webui/utils/middleware.py parsed <$skillId|label> skill mentions with overlapping quantifiers, allowing an authenticated chat message containing <$ without a closing > to trigger quadratic backtracking and block the asyncio event loop. This issue is fixed in version 0.10.0. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-59220? +

CVE-2026-59220 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 0.0032, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-59220? +

CVE-2026-59220 affects products from openwebui, specifically: open_webui. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-59220? +

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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