K33101555 : Nettle cryptography library vulnerability CVE-2021-20305

Security Advisory Description

A flaw was found in Nettle in versions before 3.7.2, where several Nettle signature verification functions (GOST DSA, EDDSA & ECDSA) result in the Elliptic Curve Cryptography point (ECC) multiply function being called with out-of-range scalers, possibly resulting in incorrect results. This flaw allows an attacker to force an invalid signature, causing an assertion failure or possible validation. The highest threat to this vulnerability is to confidentiality, integrity, as well as system availability. (CVE-2021-20305)

Impact

A flaw in the low level cryptography library code may cause the Unbound DNS server used for the DNS caching feature to become unstable. This vulnerability only affects systems that have DNS caching configured. F5 is not aware of any exploit methods that can take advantage of this vulnerability; therefore, the vulnerability is currently only a theoretical threat.