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VulnerabilityPublished

CVE-2026-121737: Facebook proxygen · Use After Free

Affects Facebook proxygenSource CVE Database V5

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Not known to be exploited : upgrade to v2026.11.09.00 soon.

Data as of 11 Nov 2026, 17:30 UTC

Severity
High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none
Patch
Available – fixed in v2026.11.09.00

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

What to do

Upgrade Facebook proxygen to v2026.11.09.00.

Affected software

ProductAffectedFixed in
FacebookproxygenAffected
  • <2026.11.09.00
Fixed in
  • v2026.11.09.00

AI-suggested

A fix is available in proxygen version v2026.11.09.00. Users should upgrade to this version or later to remediate the vulnerability. No other mitigation or workaround is indicated.

Description

CVE-2026-121737 is a use-after-free vulnerability in Facebook's proxygen HTTP library. It occurs when an unauthenticated HTTP/1.1 client pipelines a second request and then stops reading, causing proxygen's coroutine-based HTTP session to free the pipelined stream during a write timeout reset and subsequently use the freed memory. This can crash the server, resulting in denial of service, and may lead to memory corruption with further impact. The issue affects proxygen versions prior to v2026.11.09.00.

References

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