GHSA-q2xc-rrxj-58x9
Suggest an improvement- Source
- https://github.com/advisories/GHSA-q2xc-rrxj-58x9
- Import Source
- https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-q2xc-rrxj-58x9/GHSA-q2xc-rrxj-58x9.json
- JSON Data
- https://api.osv.dev/v1/vulns/GHSA-q2xc-rrxj-58x9
- Aliases
- Published
- 2026-10-08T17:16:39Z
- Modified
- 2026-10-08T17:31:45Z
- Severity
-
- 6.4 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:L CVSS Calculator
- Summary
- Pydantic AI Web chat UI (`Agent.to_web()`, `clai web`): the local chat endpoint does not validate the `Host` header
- Details
-
Summary
The Pydantic AI development web chat UI (
Agent.to_web(),clai web) does not validate theHostheader of incoming requests. A website a developer visits can use DNS rebinding to make requests to a chat UI running on that developer's machine appear same-origin to the browser, causing the served agent to run and to execute its tools with the privileges and credentials of the local process.Details
Once a name the attacker controls resolves to the loopback address, the browser treats the request as same-origin, so neither an
Origincheck nor a CSRF token constrains it — a same-origin page can read the served UI and any token in it.Binding the web UI to localhost — the default — does not prevent this.
Impact
Applications and developers serving an agent through
Agent.to_web()orclai web. The consequences depend on the tools the served agent exposes, and can include data disclosure as well as unwanted tool side effects.Current browser protections reduce but do not remove this exposure: Chromium's Local Network Access gates loopback subresource requests, but does not cover top-level navigations, and Safari does not implement it.
Mitigation
Upgrade to
pydantic-ai/pydantic-ai-slim>= 2.30.0, or >= 1.107.5 on the v1 maintenance line.The fix validates the
Hostheader and rejects anything other than localhost, a loopback/LAN IP address, or an explicitly allowed host, responding421 Misdirected Requestotherwise. If you serve the web chat UI under a real hostname — behind a reverse proxy, tunnel, or similar — name it explicitly:app = agent.to_web(allowed_hosts=['ui.example.com']) - Database specific
{ "cwe_ids": [ "CWE-346", "CWE-350" ], "github_reviewed": true, "github_reviewed_at": "2026-10-08T17:16:39Z", "nvd_published_at": null, "severity": "MODERATE" }- References
-
- https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-q2xc-rrxj-58x9
- https://github.com/pydantic/pydantic-ai/pull/7437
- https://github.com/pydantic/pydantic-ai/pull/7438
- https://github.com/pydantic/pydantic-ai/commit/394cc1d31656620704a703a2daed752afa5135fe
- https://github.com/pydantic/pydantic-ai/commit/871c7aeec5dfed2138655ccbccbf15c6d763bae7
- https://github.com/pydantic/pydantic-ai
- https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.5
- https://github.com/pydantic/pydantic-ai/releases/tag/v2.30.0
Affected packages
PyPI / pydantic-ai
Package
- Name
- pydantic-ai
- View open source insights on deps.dev
- Purl
- pkg:pypi/pydantic-ai
Affected versions
1.*
PyPI / pydantic-ai
Package
- Name
- pydantic-ai
- View open source insights on deps.dev
- Purl
- pkg:pypi/pydantic-ai
Affected versions
2.*
PyPI / pydantic-ai-slim
Package
- Name
- pydantic-ai-slim
- View open source insights on deps.dev
- Purl
- pkg:pypi/pydantic-ai-slim
Affected versions
1.*
PyPI / pydantic-ai-slim
Package
- Name
- pydantic-ai-slim
- View open source insights on deps.dev
- Purl
- pkg:pypi/pydantic-ai-slim