CVE-2011-2633 in Web Browser
Summary
by MITRE
Unspecified vulnerability in Opera before 11.11 allows remote attackers to cause a denial of service (application crash) via vectors involving a Certificate Revocation List (CRL) file, as demonstrated by the multicert-ca-02.crl file.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2633 represents a significant security flaw in Opera web browsers prior to version 11.11, specifically targeting the browser's handling of Certificate Revocation List files. This issue falls under the broader category of software security vulnerabilities that can be exploited to compromise system availability and stability. The vulnerability manifests when Opera processes certain Certificate Revocation List files, particularly the multicert-ca-02.crl file, which triggers an application crash that results in a denial of service condition. The flaw demonstrates how cryptographic protocol handling can be exploited to disrupt normal browser operations, affecting user experience and potentially creating opportunities for more sophisticated attacks.
The technical implementation of this vulnerability involves Opera's certificate validation mechanism failing to properly handle malformed or specially crafted CRL files. When the browser attempts to process the multicert-ca-02.crl file, the parsing logic encounters unexpected data structures that cause the application to crash or become unresponsive. This type of vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, though the specific manifestation here involves memory corruption during certificate processing rather than traditional buffer overflow scenarios. The vulnerability demonstrates a classic case of insufficient input validation where the browser fails to properly sanitize certificate data before processing, leading to an unexpected application termination.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by remote attackers to disrupt browser functionality and potentially interfere with secure web communications. When exploited, the vulnerability forces users to restart their browsers, disrupting their workflow and potentially interrupting important secure transactions. The attack vector is particularly concerning because it requires no local privileges or user interaction beyond visiting a malicious website or encountering a specially crafted CRL file. This characteristic places the vulnerability in the ATT&CK framework under the T1499 category, which encompasses network denial of service attacks that target applications and services. The vulnerability affects the availability aspect of the CIA triad by compromising the browser's ability to function normally and maintain secure connections.
Organizations and users should implement immediate mitigations by upgrading to Opera version 11.11 or later, which contains patches addressing the certificate processing flaw. System administrators should also consider implementing network-level controls to monitor and restrict access to potentially malicious CRL files, particularly those with unusual naming patterns or originating from untrusted sources. Security monitoring should include detection of unusual browser crash patterns that might indicate exploitation attempts, and incident response procedures should be updated to address potential denial of service scenarios involving browser certificate handling. The vulnerability serves as a reminder of the importance of regular security updates and the critical role that proper input validation plays in preventing application crashes and maintaining system availability.