CVE-2016-7098 in wget
Summary
by MITRE
Race condition in wget 1.17 and earlier, when used in recursive or mirroring mode to download a single file, might allow remote servers to bypass intended access list restrictions by keeping an HTTP connection open.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability identified as CVE-2016-7098 represents a significant race condition flaw in the wget utility affecting versions 1.17 and earlier. This vulnerability specifically manifests when wget operates in recursive or mirroring modes while downloading a single file, creating a window of opportunity for remote servers to circumvent access control mechanisms that administrators have implemented. The core issue stems from the timing discrepancy between when wget establishes connections and processes access restrictions, allowing malicious servers to manipulate the download process through persistent HTTP connections.
The technical implementation of this race condition exploits the sequence in which wget handles HTTP connections and access list validation. When wget initiates a recursive download operation, it maintains connections to remote servers to optimize transfer efficiency. However, this connection persistence creates a temporal gap where access controls are not consistently enforced, particularly during the period when a server might attempt to bypass restrictions by keeping connections open. This flaw is particularly dangerous because it operates at the protocol level, leveraging HTTP connection management rather than exploiting application-level vulnerabilities.
From an operational impact perspective, this vulnerability undermines the security posture of systems that rely on wget for automated downloads and mirroring operations. Administrators who have configured access lists to restrict file downloads from specific servers or IP ranges may find these protections circumvented without detection. The vulnerability affects organizations that use wget in automated scripts, backup operations, or content mirroring scenarios where recursive downloading is common. Attackers could potentially gain access to restricted resources that should be protected by network access controls, making this a critical concern for enterprise environments and security-conscious organizations.
The vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) flaws, and demonstrates characteristics consistent with ATT&CK technique T1071.004 for application layer protocol usage. The race condition creates an opportunity for privilege escalation and unauthorized data access, as the timing discrepancy allows malicious servers to manipulate the download process. Organizations implementing security controls around file transfer operations may experience unexpected access violations, potentially leading to data exposure or unauthorized system access. The impact extends beyond simple file access, as this vulnerability could enable attackers to bypass network security controls and potentially access sensitive data that should be restricted to authorized users only.
Mitigation strategies should focus on immediate version upgrades to wget 1.18 or later, which contain fixes addressing the race condition. Organizations should also implement additional monitoring for unusual download patterns or connection behaviors that might indicate exploitation attempts. Network administrators should consider implementing more granular access controls and connection limiting measures to reduce the impact of potential exploitation. Regular security assessments of automated download processes and file transfer operations should be conducted to identify similar timing-based vulnerabilities. The fix implemented in newer wget versions addresses the underlying connection management logic to ensure that access restrictions are consistently enforced throughout the entire download process, eliminating the temporal window that previously allowed bypass attempts.