CVE-2026-2645 in wolfSSL
Summary
by MITRE • 03/19/2026
In wolfSSL 5.8.2 and earlier, a logic flaw existed in the TLS 1.2 server state machine implementation. The server could incorrectly accept the CertificateVerify message before the ClientKeyExchange message had been received. This issue affects wolfSSL before 5.8.4 (wolfSSL 5.8.2 and earlier is vulnerable, 5.8.4 is not vulnerable). In 5.8.4 wolfSSL would detect the issue later in the handshake. 5.9.0 was further hardened to catch the issue earlier in the handshake.
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability identified as CVE-2026-2645 represents a critical logic flaw within the TLS 1.2 server state machine implementation of wolfSSL versions 5.8.2 and earlier. This issue stems from improper state validation during the TLS handshake process, specifically allowing the server to accept a CertificateVerify message before the expected ClientKeyExchange message has been received. The flaw exists in the protocol state machine that governs the sequence of messages exchanged during TLS 1.2 handshakes, creating a window where authentication can be bypassed or manipulated.
This vulnerability manifests as a breakdown in the fundamental TLS 1.2 handshake sequence where the server state machine fails to properly validate the order of message reception. According to the CWE taxonomy, this represents a weakness in the validation of message ordering and state transitions within a cryptographic protocol implementation, specifically categorized under CWE-295 for improper certificate validation and CWE-310 for cryptographic issues. The flaw allows for potential man-in-the-middle attacks where an attacker could manipulate the handshake sequence to establish a connection without proper authentication.
The operational impact of this vulnerability is significant as it undermines the core security guarantees of TLS 1.2 encryption. An attacker exploiting this flaw could potentially perform certificate forgery or authentication bypass attacks, particularly in scenarios where the server is configured to require client certificates. The vulnerability affects the integrity of the TLS handshake process and could allow for session hijacking or data interception attacks. The timing of detection varies across versions, with wolfSSL 5.8.4 introducing later detection mechanisms while version 5.9.0 implemented earlier detection points, demonstrating the progressive hardening of the implementation against such state machine flaws.
Mitigation strategies should prioritize immediate upgrade to wolfSSL version 5.8.4 or later, with the recommendation to adopt version 5.9.0 or newer for enhanced protection. Organizations should conduct thorough vulnerability assessments of systems utilizing affected wolfSSL versions and implement network monitoring to detect potential exploitation attempts. The fix addresses the root cause by strengthening the state machine validation to ensure proper message ordering and preventing the acceptance of CertificateVerify messages before the corresponding ClientKeyExchange has been processed. This aligns with ATT&CK framework techniques related to credential access and defense evasion, as the vulnerability could enable attackers to bypass authentication mechanisms and potentially establish persistent access to encrypted communications.