CVE-2011-2728 in Perl
Summary
by MITRE
The bsd_glob function in the File::Glob module for Perl before 5.14.2 allows context-dependent attackers to cause a denial of service (crash) via a glob expression with the GLOB_ALTDIRFUNC flag, which triggers an uninitialized pointer dereference.
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Analysis
by VulDB Data Team • 12/21/2021
The vulnerability described in CVE-2011-2728 resides within the File::Glob Perl module, a widely used component for file system pattern matching operations. This flaw specifically affects Perl versions prior to 5.14.2 and represents a critical security issue that can be exploited to cause system instability through deliberate manipulation of glob pattern processing. The vulnerability manifests when the bsd_glob function processes certain glob expressions that incorporate the GLOB_ALTDIRFUNC flag, creating conditions that lead to system crashes and potential denial of service conditions.
The technical root cause of this vulnerability lies in an uninitialized pointer dereference within the bsd_glob function implementation. When processing glob expressions with the GLOB_ALTDIRFUNC flag, the function fails to properly initialize certain memory pointers before attempting to access them, resulting in unpredictable behavior and system crashes. This type of flaw falls under the CWE-476 category of NULL Pointer Dereference, where a pointer expected to contain a valid memory address instead points to NULL or an uninitialized memory location. The vulnerability is context-dependent because it requires specific conditions to be met, namely the use of particular glob expressions that trigger the problematic code path involving the GLOB_ALTDIRFUNC flag.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise system stability and availability. Attackers can exploit this weakness by crafting malicious glob expressions that, when processed by the affected Perl modules, cause the application to crash or terminate unexpectedly. This can lead to cascading failures in applications that rely on Perl's File::Glob functionality for file pattern matching operations, particularly in web applications, system administration tools, and automated processes. The vulnerability is particularly concerning because it can be triggered through user input or external data sources, making it a potential vector for remote exploitation in applications that process untrusted glob patterns.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, as it can be leveraged to disrupt services through system crashes. The attack surface includes any Perl application or system that utilizes the File::Glob module, particularly web applications, system utilities, and automated scripts. Organizations using affected Perl versions should prioritize immediate patching and implementation of input validation measures to prevent exploitation. The mitigation strategy involves upgrading to Perl 5.14.2 or later versions where the vulnerability has been addressed, implementing proper input sanitization for glob expressions, and monitoring for suspicious pattern matching operations that might indicate attempted exploitation. Security teams should also consider implementing application whitelisting controls and runtime protections to prevent unauthorized access to vulnerable Perl modules and functions.