CVE-2026-109300: Stored XSS in Open WebUI Markdown renderer
Open WebUI
Open WebUI is vulnerable to stored cross-site scripting via crafted tool-call details blocks processed in its Markdown renderer. Authenticated users can execute JavaScript in other viewers' browsers.
disclosed CVENo confirmed exploitation, so this record is tracked as a disclosed vulnerability and not counted as an incident. It moves into the counts if CISA or the vendor confirms exploitation. Why
- CVSS
- 5.1
- EPSS
- <0.01 · top 89% · 2026-11-13
- fix status
- Fix status unknown
- first report
- 12 Oct 2026
- last update
- 12 Oct 2026
- CVE ids
Timeline · 1
Sources · 1
Advisories and databases
- 2026-10-12CVE-2026-109300: Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting vulnerability in its Markdown renderer, which treats…NVD · nvd.nist.gov/vuln/detail/CVE-2026-109300
Titles and links belong to their publishers. The summary above is written by gcdRadar in its own words; data is CC BY-SA 4.0.
Classification
- lane
- Patch now
- AI role
- Attack on AI
- categories
- Infrastructure vulnerability
- severity
- 2 · Disclosed vulnerability
- fix status
- Fix status unknown
- targets
- Framework / tooling
- owasp llm top 10
- LLM03:2025 Supply Chain
- mitre atlas
- no technique for these categories
- dates
- happened 12 Oct 2026 · first reported 12 Oct 2026
- origin
- NVDVulnerability record from NVD / the GitHub Advisory Database. This product uses the NVD API but is not endorsed or certified by the NVD.
- record
- confidence 0.95 · created 2026-10-18 06:33Z · updated 2026-10-18 06:33Z
Lane, AI role, categories and severity come from the classifier; the OWASP and ATLAS rows are derived from the categories. How these are assigned
Copy a brief
This record as a short Markdown brief, for a ticket, a chat or a coding agent.
the brief as text
# CVE-2026-109300: Stored XSS in Open WebUI Markdown renderer https://gcdradar.vercel.app/incidents/cve-2026-109300-stored-xss-in-open-webui-markdown-renderer · AIR-2026-0298 · closed 2026-10-12 - Lane: Patch now - Severity: 2 (Disclosed vulnerability) - Fix status: Fix status unknown - First reported: 2026-10-12 - AI role: Attack on AI - Products: Open WebUI - CVE ids: CVE-2026-109300 - CVSS: 5.1 ## Summary Open WebUI is vulnerable to stored cross-site scripting via crafted tool-call details blocks processed in its Markdown renderer. Authenticated users can execute JavaScript in other viewers' browsers. ## What to do No action recorded; read the sources below and the vendor's advisory. ## Latest updates - 2026-10-12: CVE-2026-109300: Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting vulnerability in its Markdown renderer, which treats… (https://nvd.nist.gov/vuln/detail/CVE-2026-109300) ## Sources - 2026-10-12 NVD: CVE-2026-109300: Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting vulnerability in its Markdown renderer, which treats… https://nvd.nist.gov/vuln/detail/CVE-2026-109300 Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.
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AI