CVE-2021-21251
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOneDev is an all-in-one devops platform. In OneDev before version 4.0.3 there is a critical "zip slip" vulnerability. This issue may lead to arbitrary file write. The KubernetesResource REST endpoint untars user controlled data from the request body using TarUtils. TarUtils is a custom library method leveraging Apache Commons Compress. During the untar process, there are no checks in place to prevent an untarred file from traversing the file system and overriding an existing file. For a successful exploitation, the attacker requires a valid __JobToken__ which may not be possible to get without using any of the other reported vulnerabilities. But this should be considered a vulnerability in `io.onedev.commons.utils.TarUtils` since it lives in a different artifact and can affect other projects using it. This issue was addressed in 4.0.3 by validating paths in tar archive to only allow them to be in specified folder when extracted.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA directory traversal (zip slip) vulnerability exists in OneDev's TarUtils library where the untar process lacks path validation, allowing malicious tar archives to extract files outside the intended directory and overwrite system files. The vulnerability is in the KubernetesResource REST endpoint but affects any project using the io.onedev.commons.utils.TarUtils artifact.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 4.0.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify OneDev versionCheck the installed OneDev version by reviewing the application startup logs, the About page in the web interface, or the version file in the OneDev installation directory (such as pom.xml in source or a version.properties file)Affected if The installed version is less than 4.0.3
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Locate TarUtils librarySearch for the io.onedev.commons.utils.TarUtils class or TarUtils.jar file within the OneDev installation directory, typically found under the lib or WEB-INF/lib folder in a deployed instanceAffected if The TarUtils library is present in the installation
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Verify path validation absenceInspect the TarUtils source code or decompiled class to examine the untar method implementation. Look for path validation logic that checks whether extracted file paths remain within the target directory (commonly using startsWith() or canonical path comparisons)Affected if The TarUtils.untar method contains no path validation check before extracting files
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Check KubernetesResource endpoint exposureReview the OneDev REST API endpoints configuration to confirm the KubernetesResource endpoint is accessible. This endpoint is typically at /api/kubernetes/* and is used for Kubernetes integrationAffected if The KubernetesResource REST endpoint is enabled and accessible
A OneDev installation is affected if it runs a version prior to 4.0.3 and uses the TarUtils library without path validation in its untar functionality.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data4.0.3
Upgrade to OneDev version 4.0.3 or patch TarUtils to validate that extracted file paths remain within the intended target directory before extraction.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-21251 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-21251 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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