CVE-2011-4675 in Widelands
Summary
by MITRE
The pathname canonicalization functionality in io/filesystem/filesystem.cc in Widelands before 15.1 expands leading ~ (tilde) characters to home-directory pathnames but does not restrict use of these characters in strings received from the network, which might allow remote attackers to conduct absolute path traversal attacks and overwrite arbitrary files via a ~ in a pathname that is used for a file transfer in an Internet game, a different vulnerability than CVE-2011-1932.
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Analysis
by VulDB Data Team • 02/13/2019
The vulnerability described in CVE-2011-4675 affects the Widelands game engine version 15.1 and earlier, specifically within the filesystem handling component located in io/filesystem/filesystem.cc. This flaw represents a critical path traversal vulnerability that arises from improper handling of tilde (~) character expansion in pathname canonicalization. The vulnerability is particularly concerning because it occurs during file transfer operations in internet-based multiplayer games, where network-sourced data is processed without adequate sanitization.
The technical implementation of this vulnerability stems from the fact that Widelands' filesystem component correctly expands leading tilde characters to home directory pathnames when processing local file operations. However, the same canonicalization logic fails to properly restrict or sanitize tilde characters when these strings originate from network communications. This discrepancy creates a scenario where remote attackers can craft malicious pathnames containing tilde characters that, when processed through the network-sourced file transfer mechanism, can result in unintended absolute path traversal behavior.
From an operational perspective, this vulnerability allows remote attackers to conduct absolute path traversal attacks that could potentially lead to arbitrary file overwrite operations. The attack vector specifically targets the file transfer functionality in multiplayer internet games, where players can inadvertently trigger the vulnerability by sending specially crafted filenames containing tilde characters. This creates a significant risk for game servers and clients that process untrusted network data without proper input validation, as attackers could potentially overwrite critical system files or game data.
The vulnerability's classification aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. The attack pattern follows elements of the MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1068 for exploit for privilege escalation, as successful exploitation could allow attackers to modify game files or potentially system files. The specific nature of this vulnerability differs from CVE-2011-1932, indicating a distinct path traversal implementation flaw that affects the canonicalization process rather than the file access controls.
Mitigation strategies for this vulnerability should focus on implementing strict input validation and sanitization for all network-sourced pathnames, particularly those containing special characters like tilde. The recommended approach involves rejecting or properly escaping tilde characters in network-sourced file paths before any canonicalization operations are performed. Additionally, implementing proper privilege separation between network processing and filesystem operations can help contain potential impacts. System administrators should ensure immediate patching of affected Widelands installations to version 15.1 or later, where this vulnerability has been addressed through improved path validation mechanisms and enhanced canonicalization logic that properly restricts special character usage in network-sourced pathnames.