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CRITICAL severity

CVE-2021-29940 — through

CRITICAL

CVE-2021-29940 is a critical-severity (CVSS 9.8) CWE-415 vulnerability in through. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.

Double free in through

Also known asRUSTSEC-2021-0049
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
1 known
Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk
0.00%0.61%1.22%1.83%0.5%1.3%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-29940 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 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
🦀through

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 through crate through 2021-02-18 for Rust. There is a double free (in through and through_and) upon a panic of the map function.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
🦀crates.iothroughall versionsNo fix

Affected Products

1 product · 1 configurations
Application
throughthrough_project
≤ 2021-02-18
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

An issue was discovered in the through crate through 2021-02-18 for Rust…

rustsec.orgNVDApr 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Remediation status

    No patched version of through has shipped for CVE-2021-29940 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    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 through crate through 2021-02-18 for Rust. There is a double free (in through and through_and) upon a panic of the map function.
O3 Security · Impact-Aware SCA

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CVE-2021-29940: through (Critical 9.8)