Heap-based buffer overflow in Opera before 12.11 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a long HTTP response.

Opera before 12.12 on UNIX uses weak permissions for the profile directory, which allows local users to obtain sensitive information by reading a (1) cache file, (2) password file, or (3) configuration file, or (4) possibly gain privileges by modifying or overwriting a configuration file.

Opera before 12.12 allows remote attackers to spoof the address field via a high rate of HTTP requests.

Opera before 12.12 does not properly allocate memory for GIF images, which allows remote attackers to execute arbitrary code or cause a denial of service (memory overwrite) via a malformed image.

The X.509 certificate-validation functionality in the https implementation in Opera before 12.10 allows remote attackers to trigger a false indication of successful revocation-status checking by causing a failure of a single checking service.

Cross-site scripting (XSS) vulnerability in Opera before 12.10 allows remote attackers to inject arbitrary web script or HTML via vectors involving an unspecified sequence of loading of documents and loading of data: URLs.

Opera before 12.11 allows remote attackers to determine the existence of arbitrary local files via vectors involving web script in an error page.