CVE-2026-2968 identifies a cryptographic vulnerability in Cesanta Mongoose versions 7.0 through 7.20, specifically within the mg_chacha20_poly1305_decrypt function located in /src/tls_chacha20.c. This function handles the Poly1305 authentication tag verification, a critical step in ensuring data integrity and authenticity in encrypted communications using the ChaCha20-Poly1305 AEAD cipher. The vulnerability arises from improper verification of the cryptographic signature, which could allow an attacker to bypass authentication checks or manipulate encrypted data without detection. The attack vector is remote network-based, requiring no privileges or user interaction, but exploitation complexity is high, making successful attacks challenging. Despite the difficulty, the exploit code has been publicly disclosed, increasing the risk of potential exploitation. The vendor, Cesanta, has not issued any patches or official response, leaving affected systems vulnerable. This flaw undermines the confidentiality and integrity guarantees of TLS sessions or other encrypted channels relying on this component. Given Mongoose's use in embedded and IoT devices, this vulnerability could have broad implications for secure communications in constrained environments.

The improper verification of cryptographic signatures compromises the integrity and authenticity of encrypted communications, potentially allowing attackers to inject or modify data undetected. This can lead to unauthorized data access, session hijacking, or man-in-the-middle attacks. For organizations, this threatens the confidentiality and integrity of sensitive information transmitted over networks using affected Mongoose versions. The vulnerability's remote exploitability without authentication increases the attack surface, especially for IoT devices and embedded systems that often lack robust security controls. Although exploitation is complex, the public availability of exploit code raises the risk of targeted attacks. This could impact industries relying on secure embedded communications, including telecommunications, industrial control systems, and critical infrastructure. The lack of vendor response and patches prolongs exposure, increasing potential damage and operational disruption.

1. Immediately audit all systems and devices running Cesanta Mongoose versions 7.0 through 7.20 to identify vulnerable instances. 2. Where possible, isolate affected devices from untrusted networks to reduce exposure to remote attacks. 3. Implement network-level controls such as strict firewall rules and intrusion detection systems to monitor and block suspicious traffic targeting Mongoose services. 4. Employ application-layer encryption or VPN tunnels as an additional security layer to protect data in transit beyond the vulnerable component. 5. Monitor threat intelligence feeds for updates on exploit techniques and potential patches or workarounds from Cesanta or third parties. 6. Engage with Cesanta or community forums to encourage timely patch development and share mitigation strategies. 7. For new deployments, consider alternative libraries or updated versions once patches are available. 8. Conduct thorough security testing of embedded devices incorporating Mongoose to detect any exploitation attempts or anomalous behavior.