What’s Vulnerable › Vulnerabilities

CVE-2026-59220: Open WebUI: ReDoS in skill-mention regexes causes whole-instance DoS on default config

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-09 · updated 2026-07-10
• Weakness: CWE-1333

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.

Affected products

• open-webui: from 0.9.2 before 0.10.0 — fixed in 0.10.0

How to fix

Upgrade to a fixed version: open-webui 0.10.0. Check the vendor advisory for mitigations.

References

• https://github.com/open-webui/open-webui/commit/61a26722155ec6ee1b629cf8dfcf975098c18331
• https://github.com/open-webui/open-webui/releases/tag/v0.10.0
• 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

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