Use-after-free in OpenSSL - CVE-2026-84783
Published: September 30, 2026
Vulnerability identifier: #VU152952
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-84783
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to a use-after-free in the X.509 extension cache when several threads first decode extensions for the same shared certificate. A remote attacker can cause concurrent certificate-chain construction to cause a denial of service.
The affected certificate must be a trusted CA certificate shared between connections.
Affected software
OpenSSL
How to mitigate CVE-2026-84783
Install security update from vendor's website.
OpenSSL - update to 4.0.3