CVE-2010-1989 in Web Browser
Summary
by MITRE
Opera 9.52 executes a mail application in situations where an IMG element has a SRC attribute that is a redirect to a mailto: URL, which allows remote attackers to cause a denial of service (excessive application launches) via an HTML document with many images, a related issue to CVE-2010-0181.
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Analysis
by VulDB Data Team • 09/14/2021
This vulnerability in Opera 9.52 represents a classic case of improper input validation and automatic protocol handling that can be exploited for denial of service attacks. The flaw occurs when the browser encounters an img element with a src attribute pointing to a redirect that ultimately resolves to a mailto: URL. When this happens, Opera automatically launches the default mail application without proper sanitization or rate limiting, creating a potential avenue for abuse. The vulnerability is particularly concerning because it leverages the browser's automatic handling of web content to trigger system-level actions that can be controlled by remote attackers through crafted HTML documents.
The technical mechanism behind this vulnerability involves the browser's handling of HTTP redirects combined with its automatic protocol resolution capabilities. When Opera processes an HTML document containing multiple img elements that redirect to mailto: URLs, the browser's parser does not adequately distinguish between legitimate image loading and malicious protocol triggering. This behavior stems from a lack of proper validation in the URL resolution chain, where the browser follows redirects without sufficient checks to prevent excessive application launches. The vulnerability is classified under CWE-20 as "Improper Input Validation" and specifically relates to CWE-770, "Allocation of Resources Without Limits or Throttling," as the system resources are consumed through excessive application launches. This type of vulnerability falls under the ATT&CK technique T1499.004 "Endpoint Denial of Service" where adversaries exploit resource exhaustion to prevent normal system operation.
The operational impact of this vulnerability extends beyond simple denial of service as it can be weaponized to create a cascade of unwanted application launches that consume system resources and potentially disrupt user workflows. An attacker could craft an HTML document containing numerous img elements that redirect to mailto: URLs, causing the browser to repeatedly launch the mail application. This can lead to system instability, resource exhaustion, and potentially interfere with legitimate email operations. The vulnerability is particularly dangerous in environments where users might encounter malicious content through social engineering or compromised websites, as the attack requires no special privileges beyond the ability to deliver malicious HTML content. The issue is related to CVE-2010-0181 which indicates a broader pattern of similar protocol handling flaws in the browser's security architecture. The attack vector relies on the browser's trust in redirect chains and its automatic handling of protocol schemes without proper user consent or rate limiting mechanisms.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and rate limiting mechanisms within the browser's protocol handling system. Users should be encouraged to keep their browsers updated to versions that address this specific flaw, as Opera 9.52 is an outdated version that no longer receives security updates. Browser vendors should implement stricter validation of URL redirects and establish limits on automatic protocol handling to prevent excessive application launches. The security architecture should incorporate checks to prevent recursive or excessive protocol resolution, particularly for mailto: and other system-level protocols. Organizations should consider implementing web content filtering solutions that can detect and block potentially malicious redirect chains. Additionally, users should be educated about the risks of clicking on untrusted links and visiting suspicious websites, as this vulnerability can be exploited through social engineering attacks that deliver malicious HTML content through various channels including email attachments, compromised websites, or malicious advertisements. The vulnerability highlights the importance of proper input sanitization and the need for browsers to implement robust protection mechanisms against automatic protocol handling that could be abused for denial of service attacks.