CVE-2026-58469 in wget
Summary
by MITRE • 07/07/2026
GNU Wget through 1.25.0, fixed in commit 37a40fc, contains a heap buffer underread vulnerability in the clean_metalink_string() function within src/metalink.c that allows a malicious server to trigger memory corruption by serving a Metalink document containing a whitespace-only URL. Attackers can cause the function to decrement a pointer past the start of the buffer when processing an all-whitespace Metalink URL, potentially leading to abnormal program behavior.
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Analysis
by VulDB Data Team • 07/07/2026
The vulnerability under discussion represents a critical heap buffer underread condition affecting GNU Wget versions up to 1.25.0, specifically within the clean_metalink_string() function located in src/metalink.c. This flaw stems from inadequate input validation when processing Metalink documents, which are XML-based metadata files used to describe multiple mirrors for a single file download. The issue manifests when a malicious server serves a Metalink document containing a URL that consists entirely of whitespace characters, creating a scenario where the function attempts to decrement a pointer beyond the allocated buffer boundaries.
The technical exploitation of this vulnerability occurs through the manipulation of Metalink document parsing logic where the clean_metalink_string() function fails to properly validate the length and content of URL strings before performing pointer arithmetic operations. When encountering an all-whitespace URL, the function's internal pointer management becomes compromised as it attempts to traverse backwards through memory locations that may not contain valid data, resulting in a buffer underread condition that can potentially expose sensitive memory contents or cause unpredictable program behavior. This type of vulnerability falls under CWE-129, which specifically addresses improper handling of buffer underreads, and represents a classic example of how seemingly benign input validation issues can lead to serious security consequences.
The operational impact of this vulnerability extends beyond simple program instability, as it provides attackers with a potential vector for memory corruption that could be leveraged in more sophisticated attack scenarios. When a user downloads content through wget using a Metalink document from a compromised server, the application's behavior becomes unpredictable and potentially exploitable. The underread condition may cause the program to read garbage data from adjacent memory locations, potentially exposing sensitive information such as cryptographic keys, authentication tokens, or other confidential data that happens to be stored in nearby memory regions. This vulnerability particularly affects systems where wget is used for automated downloads or when users trust unverified Metalink sources, creating a significant risk for both individual users and enterprise environments that rely on automated download mechanisms.
Mitigation strategies for this vulnerability primarily focus on immediate patch application, as the issue has been resolved through commit 37a40fc in the GNU Wget codebase. System administrators should prioritize updating to version 1.25.1 or later where the buffer underread has been properly addressed through enhanced input validation and pointer boundary checks. Additionally, organizations should implement network-level controls that restrict access to untrusted Metalink sources and consider deploying web application firewalls or proxy services that can filter and sanitize Metalink content before it reaches end-user systems. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1195.002 which covers the use of compromised credentials through malicious file downloads, emphasizing the importance of robust input validation in download utilities that process metadata files from potentially untrusted sources. The fix implemented in the patched version demonstrates proper boundary checking mechanisms that prevent pointer arithmetic from accessing memory outside the intended buffer limits, thereby eliminating the underread condition and restoring normal program execution behavior.