CVE-2026-109288 open-webui CVE debrief

Who should care

Defenders responsible for Open WebUI deployments should assess exposure and prioritize verification and remediation to prevent potential JWT theft and admin token compromise. They should review CVE and source item details for validation and focus on upgrading to Open WebUI version 0.11.4 or later. Security teams and vulnerability management teams should also be aware of the potential impacts on their environments and take appropriate actions.

Why it matters

Defenders should care about CVE-2026-109288 because it allows authenticated users to embed malicious javascript: links in shared chats, potentially leading to JWT theft and admin token compromise. Verification and remediation are necessary.

• Stealing of JWT from local storage
• Potential for admin token compromise
• Need for verification and remediation

Technical summary

The vulnerability exists in MarkdownInlineTokens.svelte, which renders markdown link URLs into anchor hrefs without validating their scheme. This allows authenticated users to embed javascript: links in shared chats that can steal the victim's JWT from local storage, including admins' tokens, when clicked. The issue requires upgrading to Open WebUI version 0.11.4 or later and monitoring for suspicious activity. The vulnerability impacts Open WebUI deployments, allowing potential JWT theft and admin token compromise.

Defensive priority

Defenders should prioritize verifying and upgrading to Open WebUI version 0.11.4 or later, and monitoring for suspicious activity.

Recommended defensive actions

• Verify Open WebUI version and upgrade to 0.11.4 or later
• Monitor for suspicious activity and embedded javascript: links
• Restrict user input and validate markdown link URLs
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability in Open WebUI before 0.11.4, which allows authenticated users to embed javascript: links in shared chats. Limited information is available on potential exploits or victims. Defenders should verify Open WebUI deployments, assess exposure, and prioritize remediation. Evidence limits suggest focusing on CVE and source item details for validation.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.