CVE-2026-43888
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 · uneditedOutline is a service that allows for collaborative documentation. Prior to 1.7.0, ZipHelper.extract computes the extraction path for each entry by passing a full filesystem path through trimFileAndExt, a filename helper that calls path.basename on its input when truncating. When a zip entry's nested path is long enough to push the joined filesystem path over MAX_PATH_LENGTH (4096 bytes), trimFileAndExt silently drops all directory components and returns a bare filename. fs.createWriteStream then opens the file relative to the process working directory instead of inside the extraction sandbox, and the escaped file persists after import cleanup because cleanupExtractedData only removes the temporary extraction directory. This vulnerability is fixed in 1.7.0.
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 zip slip vulnerability in Outline prior to 1.7.0 allows path traversal outside the extraction sandbox. When zip entries have deeply nested paths exceeding MAX_PATH_LENGTH (4096 bytes), the trimFileAndExt function drops all directory components, causing files to be written to the process working directory instead of the intended sandbox. The escaped file persists after cleanup since cleanupExtractedData only removes the temporary extraction directory.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- High
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/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 Outline versionCheck the installed Outline version by examining the application binaries, configuration files, or the application itself (typically found in About or version info)Affected if Version is prior to 1.7.0 (any 1.x.x version below 1.7.0)
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Determine if zip import is usedReview if the Outline instance has enabled or uses the document/file import feature which extracts uploaded zip archivesAffected if Zip import feature is enabled and users can upload zip archives containing nested directories
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Inspect process working directoryAfter extracting a zip with deeply nested paths (path length exceeding 4096 bytes), examine the directory where the Outline process runs for any files that should have been contained only within the extraction sandboxAffected if Files from zip extraction appear outside the intended sandbox directory in the process working directory
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Check for orphaned files post-importAfter performing a zip import operation and triggering cleanup, search the working directory for files that remain after the temporary extraction directory is removedAffected if Unexpected files persist in the working directory after import cleanup completes
A user is affected if running Outline version prior to 1.7.0 AND using the zip import feature, with files appearing outside the extraction sandbox after handling deeply nested zip archives.
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.
dbcve · scopedUpgrade to Outline version 1.7.0 or later which contains the fix for this path traversal vulnerability.
1.7.0
- Upgrade Outline to version 1.7.0 or later to remediate the path traversal vulnerability in ZipHelper.extract
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-43888 — 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-2026-43888 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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- Version or environment caveats, and links to real fixes
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