# Pydantic AI: Event loop blocked by quadratic title extraction in \`web_fetch\` Advisory record · `GHSA-fpf4-vwcp-v4hp` - **Identifiers:** `GHSA-fpf4-vwcp-v4hp` · `CVE-2026-107290` · `PYSEC-2026-4277` · `PYSEC-2026-4286` - **State:** Confirmed - **Severity:** CVSS 6.5 Medium - **Critical:** No - **Weakness (CWE):** [CWE-407](https://cwe.mitre.org/data/definitions/407.html) · [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html) - **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) - **Published:** 8 Oct 2026 - **Updated:** 15 Oct 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 8 Oct 2026, 16:48 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `pydantic-ai` (PyPI): affected `>=1.77.0, <1.107.6 || >=2.0.0b1, <2.44.0`; fixed in `1.107.6`, `2.44.0` - `pydantic-ai-slim` (PyPI): affected `>=1.77.0, <1.107.6 || >=2.0.0b1, <2.44.0`; fixed in `1.107.6`, `2.44.0` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Pydantic AI versions from 1.77.0 before 1.107.6, and from 2.0.0b1 before 2.44.0, are vulnerable, as are pydantic-ai-slim versions in the same ranges. The local web_fetch tool processes server-controlled responses in ways whose running time grows quadratically, blocking the event loop for the whole process. An attacker who can steer an agent exposed to untrusted prompts to fetch a crafted page of a megabyte or two can stall other agent runs and requests for minutes. This is an availability issue only. Upgrade to pydantic-ai 1.107.6 or 2.44.0, or pydantic-ai-slim to the same fixed versions. Written 1 Nov 2026. ## Not analysed yet We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check. ## Severity and exploitation - 6.5 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.0051, the 43rd percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 31 Oct 2026, 14:08 UTC: First seen by agentprime - 31 Oct 2026, 14:08 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-fpf4-vwcp-v4hp) ## Sources - [GitHub Advisory Database: GHSA-fpf4-vwcp-v4hp](https://github.com/advisories/GHSA-fpf4-vwcp-v4hp) - [OSV: GHSA-fpf4-vwcp-v4hp](https://osv.dev/vulnerability/GHSA-fpf4-vwcp-v4hp) - - - - - - - - - - - - Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .