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`pydantic-ai-slim` web UI `/api/chat` accepts browser-simple cross-origin requests that can trigger agent tool execution

Type: advisorySources: OSV

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 until 1.107.4 and 2.28.0, the Agent.to_web() and clai web development chat endpoint has missing request content-type validation. A website visited by a developer can submit a browser-compatible request to a loopback-hosted chat server, causing the served agent to run and execute tools with the privileges and credentials of the local process; client-relayed approval decisions also leave requires_approval=True tools exposed. Binding to localhost does not prevent a browser page from reaching the loopback address. This issue is fixed in versions 1.107.4 and 2.28.0.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-107295
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 16:25 UTC · Revision 1

Source evidence

`pydantic-ai-slim` web UI `/api/chat` accepts browser-simple cross-origin requests that can trigger agent tool execution

core-osv · Original source

Published 8 Oct 2026, 17:02 UTC

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 until 1.107.4 and 2.28.0, the Agent.to_web() and clai web development chat endpoint has missing request content-type validation. A website visited by a developer can submit a browser-compatible request to a loopback-hosted chat server, causing the served agent to run and execute tools with the privileges and credentials of the local process; client-relayed approval decisions also leave requires_approval=True tools exposed. Binding to localhost does not prevent a browser page from reaching the loopback address. This issue is fixed in versions 1.107.4 and 2.28.0.

osv:CVE-2026-107295
Complete source record
{
  "id": "558f67c27dc008a529a584d653fefc8d1c89a6f2483ac781810230405c1e4312",
  "url": "https://osv.dev/vulnerability/CVE-2026-107295",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "`pydantic-ai-slim` web UI `/api/chat` accepts browser-simple cross-origin requests that can trigger agent tool execution",
    "summary": "Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 until 1.107.4 and 2.28.0, the Agent.to_web() and clai web development chat endpoint has missing request content-type validation. A website visited by a developer can submit a browser-compatible request to a loopback-hosted chat server, causing the served agent to run and execute tools with the privileges and credentials of the local process; client-relayed approval decisions also leave requires_approval=True tools exposed. Binding to localhost does not prevent a browser page from reaching the loopback address. This issue is fixed in versions 1.107.4 and 2.28.0.",
    "evidence": "osv:CVE-2026-107295",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-107295",
      "aliases": [
        "CVE-2026-107295",
        "GHSA-h4xc-3qfq-jf93",
        "PYSEC-2026-4278",
        "PYSEC-2026-4287"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L"
        }
      ],
      "affected": [
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-107295.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.402014040Z",
      "provider": "osv",
      "references": [
        "https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.4",
        "https://github.com/pydantic/pydantic-ai/releases/tag/v2.28.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107295.json",
        "https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-h4xc-3qfq-jf93",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-107295",
        "https://github.com/pydantic/pydantic-ai/commit/d2690201a1834005d382dbf5c47e0ed94ef8bf46",
        "https://github.com/pydantic/pydantic-ai/commit/dd2abbdfa029c9ad138e7cc0edd2eaeaf9ed69c0",
        "https://github.com/pydantic/pydantic-ai/pull/7382",
        "https://github.com/pydantic/pydantic-ai/pull/7383"
      ],
      "provider_metadata": {
        "cwe_ids": [
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        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107295.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-107295",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504664,
  "published_at": "2026-10-08T17:02:36.718+00:00"
}