Summary
Cargo crates in third party registries can override the cached source of other crates
The Rust Security Response Team was notified that Cargo incorrectly handled symlinks inside of crate tarballs downloaded from third-party registries, allowing a malicious crate to override the source code of another crate from the same registry.
This vulnerability is tracked as CVE-2026-5223. The severity of the vulnerability is medium for users of third-party registries. Users of crates.io are not affected, as crates.io forbids uploading crates containing any symlink.
Overview
When building a crate, Cargo extracts its source code in a local cache (stored within ~/.cargo), reusing it for any future build. Cargo includes protections to prevent any file from being extracted outside of the crate's own cache directory.
It was discovered that it's possible to craft a malicious tarball able to extract files one level below the crate's own cache directory. With the way the cache is structured, that allowed the malicious crate to override the cache of other crates belonging to the same registry.
Mitigations
Rust 1.96.0, to be released on May 28th, 2026, will update Cargo to reject extracting any symlink within crate tarballs, regardless of whether they come from crates.io (which already forbids them) or third-party registries. Note that Cargo never added symlinks when running cargo package or cargo publish, so the impact of this should be minimal.
Users who are not able to upgrade to the most recent Rust version are recommended to audit the contents of their registry for the presence of any symlink, and to configure their registry to reject symlink (if such option is available).
Affected versions
All versions of Cargo shipped before Rust 1.96.0 are affected.
Acknowledgements
Cargo would like to thank Christos Papakonstantinou for reporting this to us according to the Rust security policy.
Cargo also wants to thank the members of the Rust project who helped address the vulnerability: Josh Triplett for developing the fix; Arlo Siemsen for reviewing the fix; Emily Albini for writing this advisory; Emily Albini, Josh Stone and Manish Goregaokar for coordinating the disclosure; Ed Page and Eric Huss for advising during the disclosure.
Impact
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-2026-5223? CVE-2026-5223 is a medium-severity security vulnerability in cargo (rust), affecting versions < 0.97.0. It is fixed in 0.97.0.
- Which versions of cargo are affected by CVE-2026-5223? cargo (rust) versions < 0.97.0 is affected.
- Is there a fix for CVE-2026-5223? Yes. CVE-2026-5223 is fixed in 0.97.0. Upgrade to this version or later.
- Is CVE-2026-5223 exploitable, and should I be worried? Whether CVE-2026-5223 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-2026-5223 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-2026-5223? Upgrade
cargoto 0.97.0 or later.