---
title: "CVE-2026-91096: proxygen - Use After Free"
description: "proxygen v2024.10.28.00 to v2026.09.28.00 contains a use-after-free vulnerability caused by failure to unregister read callbacks for closed streams in WebTransportImpl::terminateSessionStreams, letting attackers cause memory corruption or crash, exploit requires no special privileges."
url: https://panop.io/threat-heartbeat/CVE-2026-91096/
---

# CVE-2026-91096 proxygen - Use After Free

proxygen v2024.10.28.00 to v2026.09.28.00 contains a use-after-free vulnerability caused by failure to unregister read callbacks for closed streams in WebTransportImpl::terminateSessionStreams, letting attackers cause memory corruption or crash, exploit requires no special privileges.

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-2026-91096)

## Details

Type

Use After Free

Impact

Denial Of Service, Remote Code Execution

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 version v2026.09.28.00 or later.

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-2026-91096](https://nvd.nist.gov/vuln/detail/CVE-2026-91096)
- [https://www.facebook.com/security/advisories/cve-2026-91096](https://www.facebook.com/security/advisories/cve-2026-91096)
- [https://github.com/facebook/proxygen/commit/479eb5574195764e80e6cedebef669f6baa85083](https://github.com/facebook/proxygen/commit/479eb5574195764e80e6cedebef669f6baa85083)

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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

Panop answers these inside your environment, for this CVE and every other finding.

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