# Apache Fory PyFory Deserialization of Untrusted Data

Advisory record · `GHSA-m5gw-83w2-7749`

- **Identifiers:** `GHSA-m5gw-83w2-7749` · `CVE-2026-48207` · `PYSEC-2026-2984`
- **State:** Confirmed
- **Severity:** CVSS 9.8 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-502](https://cwe.mitre.org/data/definitions/502.html)
- **Tags:** [Insecure deserialization](https://agentprime.io/advisories/tag/deserialization.md)
- **Published:** 21 May 2026
- **Updated:** 13 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 21 May 2026, 18:33 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.8: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `pyfory` (PyPI): affected `>=0.13.0, <1.0.0`; fixed in `1.0.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Apache Fory PyFory versions 0.13.0 up to 1.0.0 are affected. An attacker who can supply data that an application deserializes in PyFory Python-native mode with strict mode disabled can bypass DeserializationPolicy validation hooks and may run unsafe classes, functions, or module attributes. Upgrade to pyfory 1.0.0 or later.

Written 6 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

- 9.8 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.0057, the 47th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:02 UTC: First seen by agentprime
- 31 Oct 2026, 15:02 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-m5gw-83w2-7749)

## Sources

- [GitHub Advisory Database: GHSA-m5gw-83w2-7749](https://github.com/advisories/GHSA-m5gw-83w2-7749)
- [OSV: GHSA-m5gw-83w2-7749](https://osv.dev/vulnerability/GHSA-m5gw-83w2-7749)
- <https://nvd.nist.gov/vuln/detail/CVE-2026-48207>
- <https://fory.apache.org/security/#cve-2026-48207-pyfory-reduceserializer-deserializationpolicy-bypass>
- <https://github.com/apache/fory>
- <http://www.openwall.com/lists/oss-security/2026/05/21/10>

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 (<https://api.agentprime.io/mcp>), 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: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-m5gw-83w2-7749>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-m5gw-83w2-7749/>. Everything for agents: <https://agentprime.io/llms.txt>.