CVE-2016-3180 in Browser Launcher
Summary
by MITRE
Tor Browser Launcher (aka torbrowser-launcher) before 0.2.4, during the initial run, allows man-in-the-middle attackers to bypass the PGP signature verification and execute arbitrary code via a Trojan horse tar file and a signature file with the valid tarball and signature.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-3180 affects the Tor Browser Launcher utility, specifically versions prior to 0.2.4, creating a critical security flaw during the initial execution phase of the application. This issue manifests as a man-in-the-middle attack vector that undermines the fundamental security mechanisms designed to protect users from malicious interference. The vulnerability exploits the trust relationship between the launcher and its remote resources, allowing attackers to compromise the integrity of the download process through carefully crafted malicious files. The attack specifically targets the PGP signature verification mechanism that should validate the authenticity of downloaded Tor Browser packages, effectively rendering this security control ineffective.
The technical implementation of this vulnerability relies on a Trojan horse attack pattern where an attacker positions malicious tar files and corresponding signature files on the distribution servers. When users run the Tor Browser Launcher for the first time, the application downloads these files without proper verification of their authenticity. The flaw occurs because the launcher fails to properly validate the cryptographic signatures associated with the downloaded tarballs, allowing attackers to substitute legitimate Tor Browser packages with malicious versions that appear to be properly signed. This represents a direct violation of the principle of least privilege and trust verification that security protocols require for maintaining system integrity.
The operational impact of CVE-2016-3180 extends beyond simple code execution, as it fundamentally compromises the security model that Tor Browser Launcher is designed to protect users against. Users who download and install Tor Browser through the affected launcher version become vulnerable to arbitrary code execution on their systems, potentially leading to complete system compromise. The attack vector is particularly dangerous because it targets the initial installation phase, when users are most likely to be trusting of the application's security mechanisms. This vulnerability directly relates to CWE-347, which addresses the improper verification of cryptographic signatures, and aligns with ATT&CK technique T1195.001 for 'Supply Chain Compromise - Supply Chain Injection' by exploiting the trust relationship in the software distribution chain.
Mitigation strategies for this vulnerability require immediate patching of the Tor Browser Launcher to version 0.2.4 or later, which implements proper signature verification mechanisms. Organizations and individuals should verify the integrity of downloaded packages through multiple verification methods including manual PGP key verification and cross-referencing with official Tor project release signatures. The fix addresses the underlying trust model by implementing robust verification procedures that ensure the downloaded files match the expected cryptographic signatures before execution. System administrators should also consider implementing network monitoring to detect anomalous download patterns and ensure that all users have updated to the patched version. This vulnerability underscores the critical importance of maintaining up-to-date security software and demonstrates how seemingly minor flaws in trust verification mechanisms can lead to complete system compromise.