CVE-2008-4297 in Mercurial
Summary
by MITRE
Mercurial before 1.0.2 does not enforce the allowpull permission setting for a pull operation from hgweb, which allows remote attackers to read arbitrary files from a repository via an "hg pull" request.
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability described in CVE-2008-4297 represents a critical access control flaw in Mercurial version 1.0.2 and earlier, specifically affecting the hgweb interface implementation. This issue stems from insufficient validation of user permissions during pull operations, creating a path for unauthorized data exfiltration from repositories. The flaw exists within the web-based interface that allows users to interact with Mercurial repositories through HTTP requests, fundamentally undermining the security model that should protect repository contents from unauthorized access.
The technical implementation of this vulnerability lies in the improper enforcement of the allowpull permission setting within the hgweb module. When users attempt to perform a pull operation through the web interface, the system fails to verify whether the requesting user possesses the appropriate permissions to execute such an operation. This oversight allows remote attackers to craft malicious pull requests that can traverse the file system and retrieve arbitrary files from the repository server. The vulnerability specifically affects the pull functionality rather than push operations, meaning attackers can only read files rather than modify them, but this still constitutes a significant information disclosure risk.
The operational impact of CVE-2008-4297 extends beyond simple data exposure, as it enables attackers to potentially access sensitive information stored within repositories including configuration files, source code, documentation, and potentially even credentials or private keys that may be stored in version-controlled files. This vulnerability is particularly dangerous in environments where Mercurial servers host proprietary codebases or contain sensitive organizational data, as it allows attackers to systematically enumerate and extract repository contents without proper authentication. The remote nature of this exploit means that attackers can leverage it from any location without requiring physical access to the server or prior authentication credentials.
From a cybersecurity perspective, this vulnerability aligns with CWE-284, which addresses improper access control mechanisms, and demonstrates characteristics consistent with attack patterns found in the MITRE ATT&CK framework under the privilege escalation and credential access domains. The flaw represents a classic case of insufficient authorization checks, where the system fails to properly validate user permissions before executing sensitive operations. Organizations using Mercurial servers should prioritize immediate patching to version 1.0.2 or later, which includes the necessary fixes to properly enforce the allowpull permission setting. Additionally, network segmentation, firewall rules, and access controls should be implemented to limit exposure of hgweb interfaces to untrusted networks, while monitoring systems should be configured to detect anomalous pull requests that may indicate exploitation attempts.