CVE-2026-5223
Fix: rust-lang/cargo#17031CVE-2026-5223 is a CWE-61 vulnerability in cargo. O3 Security confirms whether CVE-2026-5223 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cargo crates in third party registries can override the cached source of other crates
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-5223.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
cargoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | cargo | all versions | 0.97.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cargo. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update cargo to 0.97.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5223 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-5223 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-5223. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This Moderate vulnerability in Cargo arises from improper handling of symlinks within crate tarballs downloaded from third-party registries. An attacker could exploit this by publishing a malicious crate containing symlinks, leading to the overwrite of source code from other crates in the same registry. Red Hat…
Frequently Asked Questions
Is CVE-2026-5223 in your dependencies?
O3 detects CVE-2026-5223 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.