CVE-2026-91096: Facebook proxygen · Use After Free
Affects Facebook proxygenSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to v2026.09.28.00 soon.
Data as of 12 Nov 2026, 23:25 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 17% 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:H/I:N/A:NExploitation evidence
Disclosed: evidence found.
CVE published 28 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| Facebookproxygen | Affected
| Fixed in
|
GitHubfacebook/proxygenpkg:github/facebook/proxygenOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
CVE-2026-91096 is a use-after-free vulnerability in Facebook's proxygen library affecting versions from 2024.10.28.00 up to but not including 2026.09.28.00. The issue arises because the WebTransportImpl component fails to unregister read callbacks for streams that are no longer open before destroying them, potentially allowing the transport to invoke a freed read callback. This vulnerability has a high severity rating with a CVSS score of 7.5, indicating a significant impact on confidentiality without affecting integrity or availability.