CVE-2017-8399 in PCRE2
Summary
by MITRE
PCRE2 before 2017-03-10 has an out-of-bounds write caused by a stack-based buffer overflow in pcre2_match.c, related to a "pattern with very many captures."
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/22/2020
The vulnerability identified as CVE-2017-8399 represents a critical stack-based buffer overflow in the PCRE2 regular expression library version prior to 2017-03-10. This flaw manifests specifically within the pcre2_match.c source file and stems from inadequate input validation when processing regular expressions containing an excessive number of capturing groups. The vulnerability arises from the library's failure to properly bounds-check memory allocations when handling complex pattern structures that contain very many captures, creating a scenario where maliciously crafted regular expressions can trigger unauthorized memory writes beyond the allocated buffer boundaries.
The technical implementation of this vulnerability involves the exploitation of insufficient boundary checks during the compilation and matching phases of regular expression processing. When PCRE2 encounters a pattern with an excessive number of capturing groups, the internal memory management routines fail to validate the required buffer sizes against the actual pattern complexity. This leads to a situation where the library attempts to write data beyond the allocated stack space, potentially overwriting adjacent memory locations including return addresses, local variables, and other critical program state information. The flaw specifically relates to CWE-121 Stack-based Buffer Overflow, which is classified under the Common Weakness Enumeration framework as a fundamental memory safety issue.
The operational impact of CVE-2017-8399 extends beyond simple denial of service scenarios, as it presents significant exploitation opportunities for remote code execution attacks. Systems utilizing PCRE2 for text processing, web application firewalls, intrusion detection systems, and various security tools that depend on regular expression matching become vulnerable to attacks that could allow adversaries to execute arbitrary code with the privileges of the affected application. The vulnerability affects any software that incorporates PCRE2 libraries and processes untrusted regular expression inputs, making it particularly dangerous in web environments where users might submit malicious patterns through input fields or API endpoints. Attackers could leverage this vulnerability to bypass security controls, escalate privileges, or establish persistent access to compromised systems.
Mitigation strategies for CVE-2017-8399 require immediate patching of all affected PCRE2 installations to versions released after 2017-03-10, which contain the necessary memory bounds checking and input validation fixes. Organizations should implement regular vulnerability assessments to identify all systems utilizing PCRE2 and ensure timely updates are applied across their infrastructure. Additionally, input validation measures should be strengthened at application layers that process regular expressions, including limiting the maximum number of capturing groups allowed in user-submitted patterns and implementing proper error handling for malformed expressions. The ATT&CK framework categorizes this vulnerability under T1059 Command and Scripting Interpreter, specifically targeting the execution of arbitrary code through memory corruption techniques, making it a critical concern for enterprise security teams implementing threat detection and response protocols.