CVE-2021-4235
Denial of service in gopkg.in/yaml.v2
- Published
- Updated
- Reserved
- Assigned by
- Go
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
Timeline
ID reserved
By Go
- 5 months later
· 5 months later
Published
- 2 years later
· 2 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H |
| NVDNVD · Modified | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.43% · top 63% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Weakness
- CWE 400: Uncontrolled Resource Consumption
Affected products
gopkg.in/yaml.v2 · gopkg.in/yaml.v2
- affected < 2.2.3
github.com/go-yaml/yaml · github.com/go-yaml/yaml
All versions: affected
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/go-yaml/yamlGHSA-r88r-gmrh-7j83 (opens in a new tab)
- Gogopkg.in/yaml.v2GHSA-r88r-gmrh-7j83 (opens in a new tab)
References (4)
- https://github.com/go-yaml/yaml/pull/375 (opens in a new tab)x_transferred
- https://github.com/go-yaml/yaml/commit/bb4e33bf68bf89cad44d386192cbed201f35b241 (opens in a new tab)x_transferred
- https://pkg.go.dev/vuln/GO-2021-0061 (opens in a new tab)x_transferred
- https://lists.debian.org/debian-lts-announce/2023/07/msg00001.html (opens in a new tab)x_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-r88r-gmrh-7j83 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-4235)Record last updated .