RSA Signature Verification Vulnerability in GMP Plugin in strongSwan 4.x and 5.x before 5.7.0

CVE-2018-16151 · MEDIUM Severity

AV:N/AC:L/AU:N/C:N/I:P/A:N

In verify_emsa_pkcs1_signature() in gmp_rsa_public_key.c in the gmp plugin in strongSwan 4.x and 5.x before 5.7.0, the RSA implementation based on GMP does not reject excess data after the encoded algorithm OID during PKCS#1 v1.5 signature verification. Similar to the flaw in the same version of strongSwan regarding digestAlgorithm.parameters, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation when only an RSA signature is used for IKEv2 authentication.

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