Facebook Proxygen 2024.10.28.00/2026.07.20.00/2026.09.28.00 HTTP Session use after free

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
9.5$5k-$25k0.61+

Summaryinfo

A vulnerability classified as very critical has been found in Facebook Proxygen. Affected by this vulnerability is an unknown functionality of the component HTTP Session. The manipulation leads to use after free. This vulnerability is referenced as CVE-2026-121737. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Facebook Proxygen and classified as very critical. This issue affects some unknown processing of the component HTTP Session. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

When a remote, unauthenticated HTTP/1.1 client pipelined the start of a second request and then stopped reading, proxygen's coroutine-based HTTP session could free that pipelined stream while resetting the connection's streams on the resulting write timeout, then go on to use it. This can crash the server, leading to denial of service, and may allow memory corruption with further impact. This issue affects proxygen versions prior to v2026.11.09.00.

It is possible to read the advisory at facebook.com. The identification of this vulnerability is CVE-2026-121737 since 11/03/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 11/11/2026).

Upgrading to version 2026.11.09.00 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality 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: 10.0
VulDB Meta Temp Score: 9.5

VulDB Base Score: 10.0
VulDB Temp Score: 9.5
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 2026.11.09.00

Timelineinfo

11/03/2026 CVE reserved
11/11/2026 +8 days Advisory disclosed
11/11/2026 +0 days VulDB entry created
11/11/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: facebook.com
Status: Confirmed

CNA: Meta
CVE: CVE-2026-121737 (🔒)

GCVE (CVE): GCVE-0-2026-121737
GCVE (VulDB): GCVE-100-435875

Entryinfo

Created: 11/11/2026 18:16
Changes: 11/11/2026 18:16 (55)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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