CVE-2026-91095Network attack vectorHinoki check available

Use-after-free via stale WebTransport stream callbacks

Published Sep 28, 2026 · Updated Sep 28, 2026

Use-after-free in Meta Platforms, Inc. Proxygen allows attackers to trigger invalid memory access via WebTransport streams. HTTPTransaction returns a stream handle after its handler has ended the stream or transaction, and HQSession registers that stale handle as a QUIC read callback. This requires an application to expose WebTransport and a handler to end a stream or transaction during its callback; no crash or code execution is documented.

CVSS severityUnavailable
Unscored
EPSS probability0.25%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Use-after-free in Meta Platforms, Inc. Proxygen allows attackers to trigger invalid memory access via WebTransport streams. HTTPTransaction returns a stream handle after its handler has ended the stream or transaction, and HQSession registers that stale handle as a QUIC read callback. This requires an application to expose WebTransport and a handler to end a stream or transaction during its callback; no crash or code execution is documented.

The record

CVE
CVE-2026-91095
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

  1. Sep 28, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=v2024.10.28.00 <v2026.09.28.00

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Meta Platforms, Inc. · Proxygenversion=v2024.10.28.00 <v2026.09.28.00

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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