Vulnerability in Open-Webui
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.
Vulnerability class: ReDoS (Regular Expression Denial of Service)
EPSS: 0.004 (30.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Open-webui — versions >= 0.9.2, < 0.10.0
- Openwebui Open_webui
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-59220?
- CVE-2026-59220 is a medium-severity vulnerability in Open-Webui, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2026-07-09.
- How severe is CVE-2026-59220?
- Medium severity. CVSS v3 base score is 6.5 out of 10.