How severe is CVE-2020-36469?

CVE-2020-36469 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-36469?

CVE-2020-36469 affects the following packages: appendix (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2020-36469?

No patched version of appendix has shipped for CVE-2020-36469 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect CVE-2020-36469 in my crates.io dependencies?

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

How do I mitigate CVE-2020-36469 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2020-36469 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2020-36469, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-36469?

CVE-2020-36469 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 61th 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.

When was CVE-2020-36469 published, and has it been updated?

CVE-2020-36469 was published on August 25, 2021 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

MEDIUM severity

CVE-2020-36469 — appendix

MEDIUM

CVE-2020-36469 is a medium-severity (CVSS 5.9) vulnerability in appendix. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.

Data races in appendix

Also known asRUSTSEC-2020-0149

Published

Aug 25, 2021

Updated

Nov 8, 2023

Affected

1 pkg

Patched

See advisory

Exploits

1 known

Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs61th percentile — riskier than 61% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-36469 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 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

🦀appendix

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

The appendix crate implements a key-value mapping data structure called Index<K, V> that is stored on disk. The crate allows for any type to inhabit the generic K and V type parameters and implements Send and Sync for them unconditionally.

Using a type that is not marked as Send or Sync with Index can allow it to be used across multiple threads leading to data races. Additionally using reference types for the keys or values will lead to the segmentation faults in the crate's code.

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`appendix`	all versions	No fix

Affected Products

1 product · 1 configurations

Application

appendixappendix_project

≤ 2020-11-15

range

Exploits & PoCs

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 appendix crate through 2020-11-15 for Rus…

rustsec.orgNVDAug 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for appendix, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of appendix has shipped for CVE-2020-36469 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

The `appendix` crate implements a key-value mapping data structure called `Index<K, V>` that is stored on disk. The crate allows for any type to inhabit the generic `K` and `V` type parameters and implements Send and Sync for them unconditionally. Using a type that is not marked as `Send` or `Sync` with `Index` can allow it to be used across multiple threads leading to data races. Additionally using reference types for the keys or values will lead to the segmentation faults in the crate's code.

O3 Security · Impact-Aware SCA

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