CVE-2015-8393 in PCRE
Summary
by MITRE
pcregrep in PCRE before 8.38 mishandles the -q option for binary files, which might allow remote attackers to obtain sensitive information via a crafted file, as demonstrated by a CGI script that sends stdout data to a client.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-8393 affects the pcregrep utility within the Perl Compatible Regular Expressions library version 8.37 and earlier. This flaw specifically manifests when the utility processes files containing binary data while utilizing the quiet option (-q), creating a potential information disclosure scenario that could be exploited remotely. The issue stems from how pcregrep handles binary file content when suppressing output, leading to unintended data exposure through stdout.
The technical implementation of this vulnerability involves the improper handling of binary file data during pattern matching operations. When pcregrep encounters binary files with the -q flag, it fails to properly sanitize or filter the output stream, allowing raw binary data to be transmitted through stdout. This behavior occurs because the utility does not adequately distinguish between regular text content and binary data when processing file inputs, particularly in scenarios where the binary data contains characters that could be interpreted as valid output. The flaw is particularly concerning in web server contexts where CGI scripts might invoke pcregrep to process user-supplied input, creating a vector for attackers to extract sensitive information from system files or other binary resources.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks within web application environments. Attackers could craft malicious files containing specific binary patterns that, when processed by pcregrep, would result in sensitive data being returned to the client through HTTP responses. This scenario becomes particularly dangerous in CGI environments where pcregrep might be invoked with user-controlled input, as demonstrated by the specific attack vector involving CGI scripts. The vulnerability essentially allows for a form of data leakage where binary file contents that should remain hidden are inadvertently exposed through the program's output handling mechanism.
Security professionals should recognize this vulnerability as a variant of information disclosure issues that align with CWE-200, which covers "Information Exposure," and potentially CWE-120, "Buffer Overflow," if the binary data processing leads to memory corruption. The attack pattern follows typical remote code execution and information disclosure techniques described in the MITRE ATT&CK framework under the Information Gathering and Credential Access phases. Organizations using PCRE versions prior to 8.38 should immediately implement mitigation strategies including updating to the patched version, implementing proper input validation for CGI scripts, and monitoring for suspicious file processing patterns. Additionally, system administrators should review web server configurations to ensure that utilities like pcregrep are not being invoked with untrusted user input in contexts where output redirection might expose system information. The recommended remediation involves upgrading to PCRE version 8.38 or later, which includes proper handling of binary file content when using the quiet option, thereby preventing the unintended data exposure that characterizes this vulnerability.