CVE-2021-4239

CVE-2021-4239 affects implementations of the Noise protocol, specifically the noiseprotocol noise library. It describes two issues: a cryptographic weakness where the nonce counter wraps after 2^64 messages, leading to nonce reuse, and a denial-of-service vulnerability where failed decryption attempts desynchronize nonce states. This vulnerability carries a CVSS score of 7.5 (HIGH), indicating a network-based attack with low complexity that can lead to high integrity impact (cryptographic weakness) or denial of service. The EPSS score is very low, suggesting a minimal likelihood of exploitation. Currently, there is no evidence of active exploitation, nor are there publicly available exploit modules in Metasploit, Nuclei, or ExploitDB. Community discussion and media coverage are also absent, indicating a low level of public awareness or concern regarding this CVE.