Advisory: A forged SSL server certificate can be accepted by Opera as a valid certificate
Summary: A forged SSL server certificate can be accepted by Opera as a valid certificate.
Severity: Highly critical
Vulnerable versions: Opera for desktop computers, Opera for Windows Mobile, and other versions of Opera that use OpenSSL. See opera:about for information about third-party libraries.
A specially crafted digital certificate can bypass Opera'scertificate signature verification. Forged certificatescan contain any false information the forger chooses, andOpera will still present it as valid. Opera will not presentany warning dialogs in this case, and the security statuswill be the highest possible (3). This defeats the protectionagainst "man in the middle", the attacks that SSL was designedto prevent.
There is a flaw in OpenSSL's RSA signature verification thataffects digital certificates using 3 as the public exponent.Some of the certificate issuers that are on Opera's list oftrusted signers have root certificates with 3 as the publicexponent. The forged certificate can appear to be signed byone of these.
Opera has released version 9.02, where the signatureverification flaw in OpenSSL has been fixed.
Advisories from other vendors
Thanks to Erik Tews for notifying Opera Software aboutthis vulnerability.