CVE-2020-10878 in Communications User Data Repository
Summary
by MITRE
Perl before 5.30.3 has an integer overflow related to mishandling of a "PL_regkind[OP(n)] == NOTHING" situation. A crafted regular expression could lead to malformed bytecode with a possibility of instruction injection.
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Analysis
by VulDB Data Team • 05/19/2025
The vulnerability identified as CVE-2020-10878 represents a critical integer overflow flaw within the perl programming language implementation that affects versions prior to 5.30.3. This issue stems from improper handling of regular expression compilation logic where the interpreter fails to correctly validate array bounds when processing the PL_regkind array structure. The flaw specifically manifests when the interpreter encounters a situation where PL_regkind[OP(n)] equals NOTHING, creating a condition that allows for unpredictable behavior during bytecode generation. The integer overflow occurs during the calculation of memory allocation for compiled regular expression bytecode, where arithmetic operations exceed the maximum representable value for the integer type used in the computation.
The technical exploitation of this vulnerability requires crafting a specially designed regular expression pattern that triggers the specific code path involving the PL_regkind array manipulation. When perl processes such malformed input, the integer overflow corrupts memory layout calculations, resulting in malformed bytecode generation that can potentially allow for instruction injection attacks. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which represents a well-known class of vulnerabilities where arithmetic operations produce results that exceed the maximum value that can be represented by the target data type. The vulnerability's impact is particularly concerning because regular expressions are commonly used throughout perl applications for text processing, validation, and pattern matching, making this flaw potentially exploitable in numerous real-world scenarios.
The operational impact of CVE-2020-10878 extends beyond simple memory corruption, as it provides a potential pathway for remote code execution in environments where perl processes untrusted regular expression input. Attackers could leverage this vulnerability to inject malicious instructions into the compiled bytecode, potentially leading to arbitrary code execution on systems running vulnerable perl versions. The vulnerability's exploitation requires careful crafting of regular expressions that trigger the specific overflow condition, but given perl's widespread use in web applications, system administration tools, and network security applications, the potential attack surface is substantial. This flaw particularly affects systems where perl is used for input validation, log parsing, or any scenario involving untrusted regular expression processing, aligning with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1021.004 for Remote Services.
Organizations should prioritize immediate patching of perl installations to version 5.30.3 or later, as this represents the definitive fix for the integer overflow condition. System administrators should also implement input validation measures that sanitize all regular expression inputs, particularly in web applications where user-supplied patterns may be processed. Additional mitigations include running perl processes with reduced privileges, implementing memory protection mechanisms such as stack canaries, and monitoring for unusual memory allocation patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper integer overflow checking in interpreter implementations and highlights the need for comprehensive testing of boundary conditions in language compilers and interpreters. Security teams should also consider implementing runtime monitoring to detect anomalous bytecode generation patterns that might indicate exploitation attempts targeting this specific vulnerability.