CVE-2005-0255 in Firefox
Summary
by MITRE
String handling functions in Mozilla 1.7.3, Firefox 1.0, and Thunderbird before 1.0.2, such as the nsTSubstring_CharT::Replace function, do not properly check the return values of other functions that resize the string, which allows remote attackers to cause a denial of service and possibly execute arbitrary code by forcing an out-of-memory state that causes a reallocation to fail and return a pointer to a fixed address, which leads to heap corruption.
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Analysis
by VulDB Data Team • 03/10/2021
This vulnerability resides in the string manipulation subsystem of Mozilla applications including Firefox 1.0 and Thunderbird before version 1.0.2, specifically within the nsTSubstring_CharT::Replace function. The flaw represents a classic heap corruption vulnerability that stems from improper error handling during string operations. When string handling functions attempt to resize internal buffers through memory allocation operations, they fail to validate the success of these memory management calls, creating a pathway for malicious exploitation.
The technical mechanism of this vulnerability involves the interaction between multiple memory management functions within the Mozilla codebase. When the Replace function processes string operations that require buffer reallocation, it does not properly verify whether memory allocation succeeds. Under specific conditions, particularly when attackers craft malicious input strings that force repeated reallocations, the system can enter an out-of-memory state. When memory allocation fails in such contexts, the system returns a pointer to a fixed memory address rather than NULL or a proper error indicator, leading to heap corruption that can be exploited.
The operational impact of this vulnerability spans both denial of service and potential remote code execution capabilities. Attackers can leverage this flaw by crafting specially designed input strings that trigger the problematic code path, causing the application to crash through heap corruption or potentially execute arbitrary code if the corruption leads to controlled memory layout manipulation. This vulnerability affects widely deployed applications and represents a critical security risk for users running vulnerable versions of the Mozilla suite.
The root cause aligns with CWE-704, which addresses improper error handling in memory management operations, and demonstrates characteristics consistent with ATT&CK technique T1059 for remote code execution through memory corruption. The vulnerability specifically targets the heap management subsystem and represents a common class of flaws in string handling libraries where error propagation is not properly enforced. This type of vulnerability often requires careful input crafting to trigger the specific sequence of memory operations that lead to the exploitable state, making it particularly dangerous as it can be weaponized in targeted attacks against users of these applications.
Mitigation strategies should focus on immediate version updates to patched releases of Mozilla Firefox, Thunderbird, and related applications. Organizations should implement network-based protections including web application firewalls and input validation mechanisms that can detect and block malicious string patterns before they reach vulnerable applications. Additionally, system administrators should consider implementing memory protection mechanisms such as stack canaries and address space layout randomization to reduce exploit reliability. Regular security assessments and penetration testing should verify that applications are running patched versions and that proper input validation is in place to prevent exploitation of similar memory corruption vulnerabilities in other parts of the application stack.