CVE-2026-87994 is a medium-severity (CVSS 4.3) CWE-639 vulnerability in open-webui. O3 Security confirms whether CVE-2026-87994 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-87994.
Real-World Exposure
open-webuiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.5 until 0.11.1, the channel branch of chat_completion in backend/open_webui/main.py checked channel write access and channel membership for a supplied message_id but did not verify that the calling user authored the targeted message. A channel member could use the chat completions endpoint to replace another member's message while preserving the victim as the stored author, altering the conversation record without gaining access to other channels. This issue is fixed in version 0.11.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | open-webui | ≥ 0.9.5&&< 0.11.1 | 0.11.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for open-webui. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update open-webui to 0.11.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-87994 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-87994 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-87994. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-87994 in your dependencies?
O3 detects CVE-2026-87994 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.