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HIGH severity

CVE-2018-20993 — yaml-rust

HIGHFix: chyh1990/yaml-rust#109

CVE-2018-20993 is a high-severity (CVSS 7.5) CWE-674 vulnerability in yaml-rust. A fix is available for yaml-rust — see the affected versions and patch details below.

Uncontrolled recursion in rust-yaml

Also known asGHSA-hv87-47h9-jcvqRUSTSEC-2018-0006
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs72th percentile — riskier than 72% of all scored CVEsHighest risk
0.00%0.64%1.27%1.91%0.4%1.4%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2018-20993 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
🦀yaml-rust

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

Affected versions of this crate did not prevent deep recursion while deserializing data structures. This allows an attacker to make a YAML file with deeply nested structures that causes an abort while deserializing it. The flaw was corrected by checking the recursion depth.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioyaml-rustall versions0.4.1cargo update -p yaml-rust --precise 0.4.1

Affected Products

1 product · 1 configurations
Application
yaml-rustyaml-rust_project
< 0.4.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update yaml-rust to 0.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-20993 is resolved across your whole dependency graph.

  3. Workarounds

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

Affected versions of this crate did not prevent deep recursion while deserializing data structures. This allows an attacker to make a YAML file with deeply nested structures that causes an abort while deserializing it. The flaw was corrected by checking the recursion depth.
O3 Security · Impact-Aware SCA

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CVE-2018-20993: yaml-rust — Fixed in 0.4.1