How severe is CVE-2021-45704?

No CVSS score has been assigned to CVE-2021-45704 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2021-45704?

CVE-2021-45704 affects the following packages: metrics-util (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2021-45704?

Update metrics-util to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-45704 is resolved across your whole dependency graph.

How do I detect CVE-2021-45704 in my crates.io dependencies?

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

How do I mitigate CVE-2021-45704 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-45704 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-45704 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-45704?

CVE-2021-45704 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 53th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-45704?

CVE-2021-45704 is classified as CWE-362 (CWE-362), Out-of-bounds Write (CWE-787). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-45704 published, and has it been updated?

CVE-2021-45704 was published on June 17, 2022 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

Not in CISA KEV

CVE-2021-45704 — metrics-util

CVE-2021-45704 is a CWE-362 vulnerability in metrics-util. A fix is available for metrics-util — see the affected versions and patch details below.

AtomicBucket<T> unconditionally implements Send/Sync

Also known asGHSA-cwvc-87xq-pc5mRUSTSEC-2021-0113

Published

Jun 17, 2022

Updated

Nov 8, 2023

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 ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

🦀metrics-util

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

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::data_with() 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>).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`metrics-util`	all versions	0.7.0`cargo update -p metrics-util --precise 0.7.0`

Affected Products

1 product · 1 configurations

Application

metrics-utilmetrics-util_project

< 0.7.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for metrics-util, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update metrics-util to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-45704 is resolved across your whole dependency graph.
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

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::data_with()` 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>`).

O3 Security · Impact-Aware SCA

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