Out-of-bounds Write and Race Condition in metrics-util

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2021-45704: 0.77% estimated exploitation activity in the next 30 days; percentile 55.52 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

In the affected versions of the crate, AtomicBucket<T unconditionally implements Send/Sync traits. Therefore, users can create a data race to the inner T: !Sync by using the AtomicBucket::datawith() API. Such data races can potentially cause memory corruption or other undefined behavior. The flaw was fixed in commit 8e6daab by adding appropriate Send/Sync bounds to the Send/Sync impl of struct Block<T (which is a data type contained inside AtomicBucket<T).

Published by the source

6 Jan 2022, 22:08 UTC

Last modified by the source

13 Jun 2023, 18:14 UTC

Source last checked

26 Oct 2026, 15:34 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cwvc-87xq-pc5m

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# Patch Next advisory brief: CVE-2021-45704

Advisory: Out-of-bounds Write and Race Condition in metrics-util
IDs: CVE-2021-45704, GHSA-cwvc-87xq-pc5m
Record: https://patchnext.com/advisories/cve-2021-45704 (revision 1, source checked 26 Oct 2026, 15:34 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: metrics-util 0.7.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io metrics-util: affected < 0.7.0; fixed in 0.7.0

## Suggested inspection (read-only)
- crates.io metrics-util: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on metrics-util.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cwvc-87xq-pc5m (GitHub-reviewed advisory GHSA-cwvc-87xq-pc5m lists affected ranges: crates.io metrics-util >=0 <0.7.0)

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