Opera

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.

Problem description

A specially crafted digital certificate can bypass Opera's certificate signature verification. Forged certificates can contain any false information the forger chooses, and Opera will still present it as valid. Opera will not present any warning dialogs in this case, and the security status will be the highest possible (3). This defeats the protection against "man in the middle", the attacks that SSL was designed to prevent.

There is a flaw in OpenSSL's RSA signature verification that affects digital certificates using 3 as the public exponent. Some of the certificate issuers that are on Opera's list of trusted signers have root certificates with 3 as the public exponent. The forged certificate can appear to be signed by one of these.

Opera's response

Opera has released version 9.02, where the signature verification flaw in OpenSSL has been fixed.

Advisories from other vendors

http://www.openssl.org/news/secadv_20060905.txt

http://www.mozilla.org/security/announce/2006/mfsa2006-60.html

Credits

Thanks to Erik Tews for notifying Opera Software about this vulnerability.