CVE-1999-1111 in StackGuard
Summary
by MITRE
Vulnerability in StackGuard before 1.21 allows remote attackers to bypass the Random and Terminator Canary security mechanisms by using a non-linear attack which directly modifies a pointer to a return address instead of using a buffer overflow to reach the return address entry itself.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-1111 represents a significant weakness in the StackGuard security mechanism designed to prevent buffer overflow attacks through the use of canary values. StackGuard was developed as a compiler-based security feature that inserts random values, known as canaries, between local variables and the return address on the stack to detect and prevent stack-based buffer overflows. This particular vulnerability affects versions of StackGuard prior to 1.21 and demonstrates a sophisticated attack vector that bypasses the fundamental security assumptions of the canary mechanism.
The technical flaw exploited in this vulnerability stems from the assumption that attackers can only manipulate the stack through traditional buffer overflow techniques that overwrite the return address directly. However, the attack described in CVE-1999-1111 employs a non-linear approach that directly modifies pointer values to the return address rather than attempting to overwrite the address through buffer overflow mechanisms. This approach circumvents the canary checking mechanisms because the canary values are not directly overwritten during the attack, but rather the pointer itself is manipulated to redirect execution flow.
From an operational impact perspective, this vulnerability represents a critical security weakness that undermines the effectiveness of StackGuard as a defense-in-depth mechanism. The ability for remote attackers to bypass canary protections means that systems relying on StackGuard for stack overflow protection may be vulnerable to arbitrary code execution attacks. The non-linear nature of the attack makes it particularly dangerous because it operates outside the expected attack patterns that traditional security monitoring systems might detect. This vulnerability essentially renders the stack canary protection ineffective against sophisticated attackers who understand the underlying memory layout and can manipulate pointers directly.
The attack pattern described aligns with techniques categorized under the attack tactic of code injection and execution flow manipulation as defined by the MITRE ATT&CK framework. This vulnerability specifically relates to CWE-121, which deals with stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflows, though the particular mechanism here involves pointer manipulation rather than direct buffer overflow. The vulnerability demonstrates how sophisticated attackers can bypass compiler-level protections by understanding the underlying memory architecture and exploiting the assumptions made by security mechanisms. Organizations affected by this vulnerability should immediately upgrade to StackGuard version 1.21 or later, which implements improved canary mechanisms that detect and prevent this type of pointer-based attack. Additionally, system administrators should consider implementing additional security measures such as address space layout randomization and stack execution prevention to provide layered defense against similar attacks. The vulnerability also highlights the importance of thorough testing of security mechanisms against non-traditional attack vectors and the need for continuous security updates to address emerging threats.