Double free in OpenSSL - CVE-2026-18798
Published: August 26, 2026
Vulnerability identifier: #VU145416
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-18798
CWE-ID: CWE-415
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 double free in OpenSSL QUIC stack default packet handler when processing a malformed initial packet. A remote attacker can send a specially crafted initial packet to cause a denial of service.
The issue is triggered when channel creation fails after a QRX object is passed into connection creation, such as with a non-compliant INITIAL packet carrying a destination connection ID shorter than 8 bytes.
Affected software
OpenSSL
Debian Linux
FreeBSD
openssl (Debian package)
Debian Linux
FreeBSD
openssl (Debian package)
How to mitigate CVE-2026-18798
Install security update from vendor's website.
OpenSSL - addressed in versions 3.5.8, 3.6.4, 4.0.2
openssl (Debian package) - update to 3.5.7-1~deb13u2
openssl (Debian package) - update to 3.5.7-1~deb13u2