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VulnerabilityPublished Updated

CVE-2026-84895: Facebook proxygen · Use After Free

Affects Facebook proxygenSource CVE Database V5

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Not known to be exploited · CVSS 7.3 High : upgrade to v2026.09.28.00 soon.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
7.3High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in v2026.09.28.00, 2026.09.28.00
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 28 Sep 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 13 Nov 2026.

What to do

Upgrade proxygen to v2026.09.28.00; facebook/proxygen to 2026.09.28.00.

Affected software

ProductAffectedFixed in
FacebookproxygenAffected
  • >=2026.04.06.00 <2026.09.28.00
Fixed in
  • v2026.09.28.00
GitHubfacebook/proxygenpkg:github/facebook/proxygenOther threatsAffected
  • >=2026.04.06.00 <2026.09.28.00
Fixed in
  • 2026.09.28.00

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

CVE-2026-84895 is a use-after-free vulnerability in Facebook's proxygen library affecting versions from 2026.04.06.00 up to but not including 2026.09.28.00. The issue occurs when QuicWtSession::closeSession accesses member fields after the base class method QuicWtSessionBase::closeSession potentially destroys the session object. This can lead to memory corruption and impacts confidentiality, integrity, and availability.

References

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