#VU122079 Resource exhaustion in OpenSSL - CVE-2025-66199

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Main Vulnerability Database Vulnerabilities #VU122079

#VU122079 Resource exhaustion in OpenSSL - CVE-2025-66199

Published: January 27, 2026


Vulnerability identifier: #VU122079
Vulnerability risk: Medium
CVSSv4.0: 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/E:U/U:Green
CVE-ID: CVE-2025-66199
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability: No public exploit available
Vulnerable software:
OpenSSL
Software vendor:
OpenSSL Software Foundation

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to application does not properly control consumption of internal resources in CompressedCertificate. A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.

This issue only affects builds where TLS 1.3 certificate compression is compiled in (i.e., not OPENSSL_NO_COMP_ALG) and at least one compression algorithm (brotli, zlib, or zstd) is available, and where the compression extension is negotiated. Both clients receiving a server CompressedCertificate and servers in mutual TLS scenarios receiving a client CompressedCertificate are affected. 

Servers that do not request client certificates are not vulnerable to client-initiated attacks.


Remediation

Install updates from vendor's website.

External links