CVE-2026-3706 | mkj Dropbear up to 2025.89 S Range Check src/curve25519.c unpackneg signature verification (Issue 406 / EUVD-2026-10213)
A vulnerability, which was classified as problematic, has been found in mkj Dropbear up to 2025.89. Impacted is the function unpackneg of the file src/curve25519.c of the component S Range Check. This manipulation causes improper verification of cryptographic signature.
This vulnerability is handled as CVE-2026-3706. The attack can be initiated remotely. There is not any exploit available.
The actual existence of this vulnerability is currently in question.
To fix this issue, it is recommended to deploy a patch.
The project maintainer explains: "Signature Malleability is not exploitable in SSH protocol. (...) [A] PoC doesn't exist for SSH implementation, but rather it's against the internal API."