CVE-2026-87999 open-webui CVE debrief

Who should care

Defenders of Open WebUI instances, especially those hosted on Azure, should assess exposure and apply the patch. This includes verifying if the instance is prior to version 0.11.1 and updating accordingly. Additionally, defenders should review compensating controls for exposed systems, monitor for unauthorized access, and track exceptions and remediation efforts.

Why it matters

Defenders of Open WebUI instances should prioritize verifying exposure and applying the patch due to the potential for unauthorized access and disruption of services.

• Potential unauthorized access to sensitive information in reserved IP ranges.
• Possible disruption of services due to fetching content from unauthorized sources.
• Need for verification of instance exposure and application of the patch.

Technical summary

The vulnerability in Open WebUI allowed an authenticated user to make the instance fetch content from reserved IP ranges, such as those used by Azure. This was due to incorrect classification of Python's globally routable addresses. The issue is fixed in version 0.11.1. The vulnerability led to potential unauthorized access and disruption of services, emphasizing the need for defenders to verify exposure and apply the patch, especially for Azure-hosted instances. The fix addresses the root cause by correcting the address classification logic.

Defensive priority

Defenders should prioritize verifying exposure and applying the patch, especially for Azure-hosted instances.

Recommended defensive actions

• Verify if the instance is hosted on Azure and if the version is prior to 0.11.1.
• Apply the patch by updating to version 0.11.1 or later.
• Monitor for potential unauthorized access to reserved IP ranges.
• 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 NVD entry provide details on the vulnerability, which was fixed in version 0.11.1 of Open WebUI. The issue was related to incorrect classification of Python's globally routable addresses. The CVE record was published on 2026-09-09T22:18:48.617Z and has not been modified since then. The NVD entry provides additional information on the vulnerability and its impact.

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.