Facebook Proxygen 2026.07.20.00 WebTransport Stream onWebTransportBidiStream use after free

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.0$0-$5k0.80

Summaryinfo

A vulnerability was found in Facebook Proxygen. It has been classified as critical. This affects the function HTTPTransaction::onWebTransportUniStream/HTTPTransaction::onWebTransportBidiStream of the component WebTransport Stream Handler. This manipulation causes use after free. The identification of this vulnerability is CVE-2026-91095. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Facebook Proxygen. It has been declared as critical. Affected by this vulnerability is the function HTTPTransaction::onWebTransportUniStream/HTTPTransaction::onWebTransportBidiStream of the component WebTransport Stream Handler. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In proxygen from v2024.10.28.00 until v2026.09.28.00, the HTTPTransaction::onWebTransportUniStream and HTTPTransaction::onWebTransportBidiStream APIs could return stream handles that the stream handler had already freed. HQSession then installed those handles as transport read callbacks, which could lead to use of freed memory.

It is possible to read the advisory at facebook.com. This vulnerability is known as CVE-2026-91095 since 09/14/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/28/2026).

Upgrading to version 2026.09.28.00 eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.0

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Proxygen 2026.09.28.00

Timelineinfo

09/14/2026 CVE reserved
09/28/2026 +14 days Advisory disclosed
09/28/2026 +0 days VulDB entry created
09/28/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: facebook.com
Status: Confirmed

CVE: CVE-2026-91095 (🔒)
GCVE (CVE): GCVE-0-2026-91095
GCVE (VulDB): GCVE-100-411199

Entryinfo

Created: 09/28/2026 23:13
Changes: 09/28/2026 23:13 (56)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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