CVE-2026-107294: Pydantic AI Unbounded Memory Use When Downloading Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-v2xh-2vp8-57h8",
  "modified" : "2026-10-08T17:16:28Z",
  "published" : "2026-10-08T17:16:28Z",
  "aliases" : [ "CVE-2026-107294" ],
  "summary" : "Pydantic AI: Unbounded memory use when downloading remote content via web_fetch or FileUrl",
  "details" : "### Summary\n\nSeveral remote-content download paths in Pydantic AI buffered the entire HTTP response body into memory before enforcing any size limit. An application that exposes the local web-fetch tool (`web_fetch_tool`, or the `WebFetch` capability's local fallback) to untrusted prompts can be driven to fetch an attacker-chosen URL that streams a very large body, exhausting process memory and crashing the worker. The same unbounded buffering applied to `FileUrl` media downloads (`ImageUrl`, `DocumentUrl`, `VideoUrl`, `AudioUrl`).\n\nThis is an **availability** issue only. SSRF protections (scheme allowlist, private-IP and cloud-metadata blocking) are unaffected; there is no confidentiality or integrity impact.\n\n### Details\n\nThe download helpers read the full response body before applying content-size controls, so an existing text-length limit only truncated *after* the whole body was already in memory, and media downloads had no wire-level cap at all. A single large response could grow process memory without bound .\n\n### Who Is Affected\n\nYou are affected if your application registers the local web-fetch tool (or relies on the `WebFetch` capability's local fallback) and exposes the agent to untrusted prompts, or if it downloads large remote `FileUrl`s influenced by untrusted input. Applications that only fetch developer-controlled URLs are not exposed to the model-chosen attack path.\n\n### Remediation\n\nUpgrade to `2.24.0` or later (v2) or `1.107.2` or later (v1). Patched versions enforce a default 50 MiB cap on web-fetch and `FileUrl` downloads while streaming; pass `None` to the limit to restore the previous unbounded behavior.\n\n### Credits\n\nIdentified during internal review of media-download hardening.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pydantic-ai"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.77.0"
      }, {
        "fixed" : "1.107.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pydantic-ai"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0b1"
      }, {
        "fixed" : "2.24.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.23.0"
    }
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pydantic-ai-slim"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.77.0"
      }, {
        "fixed" : "1.107.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pydantic-ai-slim"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0b1"
      }, {
        "fixed" : "2.24.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.23.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-v2xh-2vp8-57h8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/pull/7141"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/pull/7308"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/commit/7a64d049c3f5271a975cd1d64b2fa876d83ede1d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/commit/e3824a58c82864ed26afb2887619834a4eb86cc8"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pydantic/pydantic-ai"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pydantic/pydantic-ai/releases/tag/v2.24.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-08T17:16:28Z",
    "nvd_published_at" : null
  }
}