---
title: "CVE-2026-48207: Apache Fory PyFory Deserialization of Untrusted Data"
url: https://erroneo.us/security/cve/CVE-2026-48207/
description: "CVE-2026-48207 (pyfory (PyPI)): Deserialization of untrusted data in Apache Fory PyFory. PyFory's ReduceSerializer could bypass documented…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-21
date_modified: 2026-06-30
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-48207"
kev: false
cvss: 9.8
epss: 0.00817
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-48207: Apache Fory PyFory Deserialization of Untrusted Data

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.8% , percentile 57: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 57% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes pyfory (PyPI) >= 0.13.0, < 1.0.0, fixed in 1.0.0 . Check your lockfile, including transitive dependencies.

## What it is

Deserialization of untrusted data in Apache Fory PyFory. PyFory's ReduceSerializer could bypass documented DeserializationPolicy validation hooks during reduce-state restoration and global-name resolution. An application is vulnerable if it deserializes attacker-controlled data using PyFory Python-native mode with strict mode disabled and relies on DeserializationPolicy to restrict unsafe classes, functions, or module attributes. This issue affects Apache Fory: from before 1.0.0. Mitigation: Users of Apache Fory are recommended to upgrade to version 1.0.0 or later, which enforces DeserializationPolicy validation for the affected ReduceSerializer paths and thus fixes this issue.

## Affected packages

- PyPI `pyfory` >= 0.13.0, < 1.0.0 → fixed: 1.0.0

## Affected products (CVE record)

- Apache Software Foundation Apache Fory: 0.13.0 < 1.0.0

## Severity

- CISA-ADP CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.82% probability of exploitation activity in the next 30 days; percentile 57.

## Sources

- [fory.apache.org](https://fory.apache.org/security/#cve-2026-48207-pyfory-reduceserializer-deserializationpolicy-bypass)
- [GitHub Advisory GHSA-m5gw-83w2-7749](https://github.com/advisories/GHSA-m5gw-83w2-7749)
- [CVE.org record CVE-2026-48207](https://www.cve.org/CVERecord?id=CVE-2026-48207)
- [NVD entry CVE-2026-48207](https://nvd.nist.gov/vuln/detail/CVE-2026-48207)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/05/21/10)

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Source page: https://erroneo.us/security/cve/CVE-2026-48207/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt