Blind Trust in ASN.1 Lengths in sig_verify() in axTLS Version 2.1.3 and Earlier

CVE-2018-16149 · MEDIUM Severity

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

In sig_verify() in x509.c in axTLS version 2.1.3 and before, the PKCS#1 v1.5 signature verification blindly trusts the declared lengths in the ASN.1 structure. Consequently, when small public exponents are being used, a remote attacker can generate purposefully crafted signatures (and put them on X.509 certificates) to induce illegal memory access and crash the verifier.

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