Use-after-free via retained WebTransport read callback
Published Sep 28, 2026 · Updated Sep 28, 2026
Use-after-free in Meta Platforms, Inc. Proxygen before 2026.09.28.00 allows attackers to invoke a freed callback via WebTransport. In affected releases beginning at 2024.10.28.00, WebTransportImpl::terminateSessionStreams destroys closed streams without first unregistering their read callbacks, leaving the transport with pointers to freed handles. Exposure requires an application using WebTransport and a closed stream with a registered read callback; the published record does not establish code execution or a specific service-interruption outcome.
Summary
What happened
Use-after-free in Meta Platforms, Inc. Proxygen before 2026.09.28.00 allows attackers to invoke a freed callback via WebTransport. In affected releases beginning at 2024.10.28.00, WebTransportImpl::terminateSessionStreams destroys closed streams without first unregistering their read callbacks, leaving the transport with pointers to freed handles. Exposure requires an application using WebTransport and a closed stream with a registered read callback; the published record does not establish code execution or a specific service-interruption outcome.
The record
- CVE
- CVE-2026-91096
- Published
- Sep 28, 2026
- Updated
- Sep 28, 2026
- Vendor
- Meta Platforms, Inc.
- Product
- Proxygen
- Classifications
- CWE-416
- Attack vector
- network
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 28, 2026CVE publishedPublication date reported by the CVE source.
- Sep 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=v2024.10.28.00 <v2026.09.28.00
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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