CVE-2021-21249

CRITICALNVD 9.69.6—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.6 under NVD CVSS v3. EPSS exploit probability: 2.9%, top 14% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
9.6
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.6Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, there is an issue involving YAML parsing which can lead to post-auth remote code execution. In order to parse and process YAML files, OneDev uses SnakeYaml which by default (when not using SafeConstructor) allows the instantiation of arbitrary classes. We can leverage that to run arbitrary code by instantiating classes such as javax.script.ScriptEngineManager and using URLClassLoader to load the script engine provider, resulting in the instantiation of a user controlled class. For a full example refer to the referenced GHSA. This issue was addressed in 4.0.3 by only allowing certain known classes to be deserialized

CVSS v3
9.6
EG Score
9.6(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity96% × 45%
Exploitation3% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
85.6%
KEV
Not listed

Published

January 15, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Jul 15, 2026
Patch available. Sources: github_commit, github.
github Patch Available

Post-Auth Unsafe Yaml deserialization · Advisory · theonedev/onedev · GitHub

https://github.com/theonedev/onedev/security/advisories/GHSA-7xhq-m2q9-6hpm
github_commit Patch Available

commit d6fc4212b1ac (theonedev/onedev)

Patch available: theonedev/onedev v14.1.7 (contains commit d6fc4212b1ac)

https://github.com/theonedev/onedev/commit/d6fc4212b1ac1e9bbe3ce444e95f9af1e3ab8b66

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

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  75. 2026-05-24 16:49 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-21249?
CVE-2021-21249 is a critical vulnerability published on January 15, 2021. OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, there is an issue involving YAML parsing which can lead to post-auth remote code execution. In order to parse and process YAML files, OneDev uses SnakeYaml which by default (when not using SafeConstructor) allows the…
When was CVE-2021-21249 disclosed?
CVE-2021-21249 was first published in the National Vulnerability Database on January 15, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21249 actively exploited?
CVE-2021-21249 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 85.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21249?
CVE-2021-21249 has a CVSS v3 base score of 9.6 (NVD).
How do I remediate CVE-2021-21249?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21249, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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