What’s Vulnerable › Vulnerabilities

CVE-2021-4235: Denial of service in gopkg.in/yaml.v2

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2022-12-27 · updated 2026-06-17

Description

Due to unbounded alias chasing, a maliciously crafted YAML file can cause the system to consume significant system resources. If parsing user input, this may be used as a denial of service vector.

Affected products

• gopkg.in/yaml.v2: before 2.2.3 — fixed in 2.2.3
• Go Github.Com/Go-Yaml/Yaml: all versions
• Gopkg.In/Yaml.V2: before 2.2.3 — fixed in 2.2.3

How to fix

Upgrade to a fixed version: gopkg.in/yaml.v2 2.2.3; Gopkg.In/Yaml.V2 2.2.3. Check the vendor advisory for mitigations.

References

• https://github.com/go-yaml/yaml/commit/bb4e33bf68bf89cad44d386192cbed201f35b241
• https://github.com/go-yaml/yaml/pull/375
• https://lists.debian.org/debian-lts-announce/2023/07/msg00001.html
• https://pkg.go.dev/vuln/GO-2021-0061
• https://github.com/go-yaml/yaml/commit/bb4e33bf68bf89cad44d386192cbed201f35b241
• https://github.com/go-yaml/yaml/pull/375
• https://lists.debian.org/debian-lts-announce/2023/07/msg00001.html
• https://pkg.go.dev/vuln/GO-2021-0061

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