---
title: "CVE-2026-84894: moxygen - Use After Free"
description: "moxygen before commit 004123dd24c3 contains a use-after-free caused by MoQSession::dataStreamReadLoop using a stream read handle after reading a FIN under proxygen's WebTransport API, letting remote attackers trigger stale handle use, exploit requires opening a data stream with an unknown track alias and FIN in the same write."
url: https://panop.io/threat-heartbeat/CVE-2026-84894/
---

# CVE-2026-84894 moxygen - Use After Free

moxygen before commit 004123dd24c3 contains a use-after-free caused by MoQSession::dataStreamReadLoop using a stream read handle after reading a FIN under proxygen's WebTransport API, letting remote attackers trigger stale handle use, exploit requires opening a data stream with an unknown track alias and FIN in the same write.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.26% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-84894)

## Details

Type

Use After Free

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Published

28 September 2026

Updated

15 October 2026

Weakness

[CWE-416](https://cwe.mitre.org/data/definitions/416.html)

## Vendor fix

Update to the version after commit 004123dd24c3 or latest available version.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-84894](https://nvd.nist.gov/vuln/detail/CVE-2026-84894)
- [https://github.com/facebookexperimental/moxygen/commit/004123dd24c30dad6b649163575145f240dabc94](https://github.com/facebookexperimental/moxygen/commit/004123dd24c30dad6b649163575145f240dabc94)
- [https://www.facebook.com/security/advisories/cve-2026-84894](https://www.facebook.com/security/advisories/cve-2026-84894)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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