What’s Vulnerable › Vulnerabilities

CVE-2020-15254: Undefined Behavior in bounded Crossbeam channel

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-10-16 · updated 2026-06-17
• Weakness: CWE-119

Description

Crossbeam is a set of tools for concurrent programming. In crossbeam-channel before version 0.4.4, the bounded channel incorrectly assumes that `Vec::from_iter` has allocated capacity that same as the number of iterator elements. `Vec::from_iter` does not actually guarantee that and may allocate extra memory. The destructor of the `bounded` channel reconstructs `Vec` from the raw pointer based on the incorrect assumes described above. This is unsound and causing deallocation with the incorrect capacity when `Vec::from_iter` has allocated different sizes with the number of iterator elements. This has been fixed in crossbeam-channel 0.4.4.

Affected products

• crossbeam-rs crossbeam: before 0.4.4 — fixed in 0.4.4

How to fix

Upgrade to a fixed version: crossbeam-rs crossbeam 0.4.4. Check the vendor advisory for mitigations.

References

• https://github.com/RustSec/advisory-db/pull/425
• https://github.com/crossbeam-rs/crossbeam/issues/539
• https://github.com/crossbeam-rs/crossbeam/pull/533
• https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-v5m7-53cv-f3hx
• https://github.com/RustSec/advisory-db/pull/425
• https://github.com/crossbeam-rs/crossbeam/issues/539
• https://github.com/crossbeam-rs/crossbeam/pull/533
• https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-v5m7-53cv-f3hx

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