CVE-2017-12883 in Perl
Summary
by MITRE
Buffer overflow in the regular expression parser in PERL before 5.24.3-RC1 and 5.26.x before 5.26.1-RC1 allows remote attackers to cause a denial of service (crash) or leak data from memory via vectors involving use of RExC_parse in the vFAIL macro.
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Analysis
by VulDB Data Team • 01/13/2021
The vulnerability identified as CVE-2017-12883 represents a critical buffer overflow flaw within the regular expression parser of the perl programming language. This issue affects perl versions prior to 5.24.3-RC1 and 5.26.x versions before 5.26.1-RC1, creating a significant security risk for systems that rely on perl for text processing and pattern matching operations. The vulnerability specifically manifests in the RExC_parse variable handling within the vFAIL macro, which is a fundamental component of perl's regular expression compilation and execution engine.
The technical nature of this flaw stems from improper bounds checking during regular expression parsing operations. When perl processes certain malformed regular expressions, particularly those involving complex patterns or specific character sequences, the RExC_parse variable becomes susceptible to buffer overflows. This occurs because the parser does not adequately validate the size of data structures when handling the vFAIL macro, which is used for error handling and pattern matching failures. The overflow conditions can be triggered through carefully crafted regular expressions that exploit memory layout assumptions within the perl interpreter.
The operational impact of CVE-2017-12883 extends beyond simple denial of service to potentially enable data leakage from system memory. Remote attackers can leverage this vulnerability to crash perl processes, causing denial of service conditions that disrupt legitimate system operations. More concerning is the potential for information disclosure, where attackers might be able to extract sensitive data from memory locations that should remain protected. This makes the vulnerability particularly dangerous in web applications, network services, or any system where perl processes user-supplied input through regular expression operations, as it could lead to exposure of confidential information or system internals.
This vulnerability aligns with CWE-121, which describes buffer overflow conditions in stack-based buffers, and represents a classic example of improper input validation in parsing components. From an attacker perspective, the flaw maps to ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting perl interpreter execution environments. The vulnerability demonstrates how parsing components in scripting languages can become attack vectors when insufficient bounds checking is implemented. Organizations using perl for web applications, network services, or automated processing should prioritize patching this vulnerability to prevent potential exploitation, as the combination of remote code execution potential and information disclosure capabilities makes it a high-priority security concern. The fix implemented in perl 5.24.3-RC1 and 5.26.1-RC1 involved strengthening bounds checking and memory management within the regular expression parser to prevent the overflow conditions that previously allowed for system instability and potential data leakage.