CVE-2018-6797 in macOS
Summary
by MITRE
An issue was discovered in Perl 5.18 through 5.26. A crafted regular expression can cause a heap-based buffer overflow, with control over the bytes written.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability identified as CVE-2018-6797 represents a critical heap-based buffer overflow in Perl versions ranging from 5.18 through 5.26. This flaw exists within the regular expression engine's handling of specially crafted patterns that can lead to memory corruption. The vulnerability stems from improper bounds checking during the processing of regular expressions, particularly when dealing with complex pattern matching operations that involve heap memory allocation. The issue manifests when Perl's regex engine encounters malformed patterns that cause it to write beyond the allocated buffer boundaries, potentially allowing attackers to overwrite adjacent memory regions with controlled data.
The technical implementation of this vulnerability involves the manipulation of Perl's internal regex compilation and execution mechanisms. When processing certain regular expressions, the engine allocates heap memory for pattern matching operations but fails to properly validate the size requirements for buffer allocations. This allows an attacker to craft malicious regex patterns that cause the engine to write data beyond the intended buffer limits, potentially overwriting heap metadata or adjacent memory segments. The control over bytes written provides attackers with significant flexibility in crafting payloads that could lead to arbitrary code execution or denial of service conditions.
From an operational perspective, this vulnerability poses substantial risks to systems running affected Perl versions, particularly those that process untrusted input through regex operations. The vulnerability can be exploited in web applications, scripting environments, and any system where Perl is used to handle user-provided data through regular expression matching. Attackers can leverage this flaw to execute remote code on vulnerable systems, potentially leading to complete system compromise. The impact extends beyond simple denial of service as the heap corruption can be carefully crafted to overwrite function pointers, return addresses, or other critical memory structures, enabling arbitrary code execution.
The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and more specifically relates to heap-based buffer overflows that can be exploited through memory corruption techniques. From an attack framework perspective, this vulnerability maps to multiple ATT&CK techniques including T1059 for command and script injection and T1070 for indicator removal. The exploitation requires minimal privileges and can be automated through web-based interfaces, making it particularly dangerous in multi-tenant environments or shared hosting platforms. Organizations should prioritize patching affected systems and implementing input validation measures to prevent exploitation, as the vulnerability can be triggered through simple regex pattern processing without requiring complex attack chains.
Mitigation strategies should include immediate patching of all affected Perl installations to versions that contain the fix for this buffer overflow vulnerability. Additionally, organizations should implement strict input validation and sanitization for all regex operations, particularly when processing untrusted data. Runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures, though they may not prevent exploitation entirely. System administrators should monitor for suspicious regex patterns in logs and implement web application firewalls to detect and block potentially malicious input patterns that could trigger this vulnerability. Regular security assessments and penetration testing should include verification of patched status to ensure complete remediation of this memory corruption vulnerability across all affected systems.