What’s Vulnerable › Vulnerabilities

CVE-2021-41110: CWL Viewer: deserialization of untrusted data can lead to complete takeover by an attacker

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.8% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-10-01 · updated 2026-06-17
• Weakness: CWE-502

Description

cwlviewer is a web application to view and share Common Workflow Language workflows. Versions prior to 1.3.1 contain a Deserialization of Untrusted Data vulnerability. Commit number f6066f09edb70033a2ce80200e9fa9e70a5c29de (dated 2021-09-30) contains a patch. There are no available workarounds aside from installing the patch. The SnakeYaml constructor, by default, allows any data to be parsed. To fix the issue the object needs to be created with a `SafeConstructor` object, as seen in the patch.

Affected products

• common-workflow-language cwlviewer: before 1.3.1 — fixed in 1.3.1

How to fix

Upgrade to a fixed version: common-workflow-language cwlviewer 1.3.1. Check the vendor advisory for mitigations.

References

• https://github.com/common-workflow-language/cwlviewer/commit/f6066f09edb70033a2ce80200e9fa9e70a5c29de
• https://github.com/common-workflow-language/cwlviewer/security/advisories/GHSA-7g7j-f5g3-fqp7
• https://www.fatalerrors.org/a/analysis-of-the-snakeyaml-deserialization-in-java-security.html
• https://github.com/common-workflow-language/cwlviewer/commit/f6066f09edb70033a2ce80200e9fa9e70a5c29de
• https://github.com/common-workflow-language/cwlviewer/security/advisories/GHSA-7g7j-f5g3-fqp7
• https://www.fatalerrors.org/a/analysis-of-the-snakeyaml-deserialization-in-java-security.html

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