Summary
Cargo did not verify SSH host keys
The Rust Security Response WG was notified that Cargo did not perform SSH host key verification when cloning indexes and dependencies via SSH. An attacker could exploit this to perform man-in-the-middle (MITM) attacks.
This vulnerability has been assigned CVE-2022-46176.
Overview
When an SSH client establishes communication with a server, to prevent MITM attacks the client should check whether it already communicated with that server in the past and what the server's public key was back then. If the key changed since the last connection, the connection must be aborted as a MITM attack is likely taking place.
It was discovered that Cargo never implemented such checks, and performed no validation on the server's public key, leaving Cargo users vulnerable to MITM attacks.
Affected Versions
All Rust versions containing Cargo before 1.66.1 are vulnerable (prior to 0.67.1 for the crates.io package).
Note that even if you don't explicitly use SSH for alternate registry indexes or crate dependencies, you might be affected by this vulnerability if you have configured git to replace HTTPS connections to GitHub with SSH (through git's url.<base>.insteadOf setting), as that'd cause you to clone the crates.io index through SSH.
Mitigations
We will be releasing Rust 1.66.1 today, 2023-01-10, changing Cargo to check the SSH host key and abort the connection if the server's public key is not already trusted. We recommend everyone to upgrade as soon as possible.
Patch files for Rust 1.66.0 are also available here for custom-built toolchains.
For the time being Cargo will not ask the user whether to trust a server's public key during the first connection. Instead, Cargo will show an error message detailing how to add that public key to the list of trusted keys. Note that this might break your automated builds if the hosts you clone dependencies or indexes from are not already trusted.
If you can't upgrade to Rust 1.66.1 yet, we recommend configuring Cargo to use the git CLI instead of its built-in git support. That way, all git network operations will be performed by the git CLI, which is not affected by this vulnerability. You can do so by adding this snippet to your Cargo configuration file:
[net]
git-fetch-with-cli = true
Acknowledgments
Thanks to the Julia Security Team for disclosing this to us according to our security policy!
We also want to thank the members of the Rust project who contributed to fixing this issue. Thanks to Eric Huss and Weihang Lo for writing and reviewing the patch, Pietro Albini for coordinating the disclosure and writing this advisory, and Josh Stone, Josh Triplett and Jacob Finkelman for advising during the disclosure.
Impact
CVE-2022-46176 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.67.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2022-46176? CVE-2022-46176 is a medium-severity security vulnerability in cargo (rust), affecting versions <= 0.67.0. It is fixed in 0.67.1.
- How severe is CVE-2022-46176? CVE-2022-46176 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of cargo are affected by CVE-2022-46176? cargo (rust) versions <= 0.67.0 is affected.
- Is there a fix for CVE-2022-46176? Yes. CVE-2022-46176 is fixed in 0.67.1. Upgrade to this version or later.
- Is CVE-2022-46176 exploitable, and should I be worried? Whether CVE-2022-46176 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-46176 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-46176? Upgrade
cargoto 0.67.1 or later.