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HIGH severity

CVE-2020-36442 — beef

HIGH

CVE-2020-36442 is a high-severity (CVSS 8.1) CWE-362 vulnerability in beef. A fix is available for beef — see the affected versions and patch details below.

Data races in beef

Also known asRUSTSEC-2020-0122
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk
0.00%0.42%0.84%1.27%0.3%0.8%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-36442 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🦀beef

Real-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

An issue was discovered in the beef crate before 0.5.0 for Rust. Affected versions of this crate did not have a T: Sync bound in the Send impl for Cow<'_, T, U>. This allows users to create data races by making Cow contain types that are (Send && !Sync) like Cell<_> or RefCell<_>.

Such data races can lead to memory corruption.

The flaw was corrected in commit d1c7658 by adding trait bounds T: Sync and T::Owned: Send to the Send impl for Cow<'_, T, U>.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iobeefall versions0.5.0cargo update -p beef --precise 0.5.0

Affected Products

1 product · 1 configurations
Application
beefbeef_project
< 0.5.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for beef, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update beef to 0.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-36442 is resolved across your whole dependency graph.

  3. Workarounds

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

An issue was discovered in the beef crate before 0.5.0 for Rust. Affected versions of this crate did not have a `T: Sync` bound in the `Send` impl for `Cow<'_, T, U>`. This allows users to create data races by making `Cow` contain types that are (Send && !Sync) like `Cell<_>` or `RefCell<_>`. Such data races can lead to memory corruption. The flaw was corrected in commit d1c7658 by adding trait bounds `T: Sync` and `T::Owned: Send` to the `Send` impl for `Cow<'_, T, U>`.
O3 Security · Impact-Aware SCA

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CVE-2020-36442: beef — Fixed in 0.5.0