Bug 2542696 (CVE-2026-91096)

Summary: CVE-2026-91096 proxygen: proxygen: Denial of Service via use-after-free in WebTransport stream termination
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in proxygen. The WebTransport implementation fails to unregister read callbacks for closed streams before destroying them. This issue results in a use-after-free condition, where the transport attempts to invoke memory that has already been released. A remote attacker can exploit this vulnerability to cause a Denial of Service (DoS) via an application crash or potentially execute arbitrary code.
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Bug Depends On: 2542964    
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Description OSIDB Bzimport 2026-09-28 20:52:28 UTC 
In proxygen from v2024.10.28.00 until v2026.09.28.00, WebTransportImpl::terminateSessionStreams (WebTransportImpl::destroy in releases before v2025.08.18.00) failed to unregister read callbacks for streams that were no longer open before destroying them. The transport could then invoke a read callback that had been freed.