CVE-2011-0419 in HTTP Server
Summary
by MITRE
Stack consumption vulnerability in the fnmatch implementation in apr_fnmatch.c in the Apache Portable Runtime (APR) library before 1.4.3 and the Apache HTTP Server before 2.2.18, and in fnmatch.c in libc in NetBSD 5.1, OpenBSD 4.8, FreeBSD, Apple Mac OS X 10.6, Oracle Solaris 10, and Android, allows context-dependent attackers to cause a denial of service (CPU and memory consumption) via *? sequences in the first argument, as demonstrated by attacks against mod_autoindex in httpd.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/16/2024
The CVE-2011-0419 vulnerability represents a critical stack consumption issue affecting the fnmatch pattern matching implementation across multiple operating systems and software libraries. This vulnerability specifically targets the Apache Portable Runtime library and Apache HTTP Server implementations where the fnmatch function processes wildcard patterns containing *? sequences. The flaw manifests when these pattern matching functions encounter certain combinations of wildcards in the first argument, leading to exponential stack growth during processing. The vulnerability operates within the context of web server operations where mod_autoindex module utilizes fnmatch for directory listing pattern matching, making it particularly dangerous in web server environments.
The technical implementation of this vulnerability stems from the recursive nature of the fnmatch algorithm in the affected implementations. When processing patterns containing *? sequences, the function enters into deeply nested recursive calls that consume stack space proportional to the input pattern length. This creates a situation where an attacker can craft malicious patterns that cause the stack to grow exponentially, eventually exhausting available stack memory and leading to process termination. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption, specifically involving stack memory exhaustion. The implementation flaw occurs in the apr_fnmatch.c file where the pattern matching logic fails to properly bound recursive calls or implement iterative alternatives that could prevent unbounded stack growth.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited to consume significant system resources and potentially cause system instability. Attackers can leverage this vulnerability by constructing malicious directory listing patterns that trigger the vulnerable code path in mod_autoindex, leading to high cpu utilization and memory consumption. The exploit demonstrates particular effectiveness against web servers where directory indexing is enabled, as the pattern matching occurs during directory listing operations. This vulnerability affects multiple platforms including NetBSD, OpenBSD, FreeBSD, Mac OS X, Oracle Solaris, and Android, indicating a widespread issue in standard system libraries. The attack vector is context-dependent meaning it requires specific conditions to be effective, typically involving web server operations with directory indexing enabled.
Mitigation strategies for CVE-2011-0419 focus on both immediate patching and defensive programming approaches. The primary solution involves updating to patched versions of affected software including APR 1.4.3 and Apache HTTP Server 2.2.18, as well as updating system libraries on affected operating systems. System administrators should disable directory indexing where possible or implement input validation to prevent malicious pattern matching sequences from reaching the vulnerable functions. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks and can be categorized under ATT&CK tactic TA0040 for resource consumption. Organizations should implement monitoring for unusual cpu and memory usage patterns that could indicate exploitation attempts. Defensive programming practices should include implementing stack depth limits or iterative pattern matching algorithms that prevent recursive explosion. The vulnerability also highlights the importance of proper input validation and bounds checking in system libraries, particularly those used in security-critical applications such as web servers and network services.