CVE-2026-77763
Received Received - Intake

Path Traversal in JuiceFS File Store

Publication date: 2026-08-21

Last updated on: 2026-08-21

Assigner: VulnCheck

Description
The filestore backend in pkg/object/file.go, used for file:// stores and as a common juicefs sync destination, derived every operation's target from path(key), which returned either filepath.Join(d.root, key) or filepath.Clean(d.root + key) with no check that the result stayed beneath the root. Put, Get, Head, Delete, Chmod, Chown, Symlink and Readlink all consumed that value directly. Object keys enumerated from a source object store during a sync are not constrained the way local filesystem names are, so a key containing traversal segments causes juicefs to write attacker-supplied content to a path outside the intended local destination, and no error is returned. An operator syncing from a bucket whose contents they do not fully control, such as a shared or public bucket or one an attacker can write to, is therefore exposed to a file write at an attacker-influenced location. The fix changes path() to return an error and rejects any key whose resolved path escapes the root.

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Meta Information

Published
2026-08-21
Last Modified
2026-08-21
Generated
2026-08-21
AI Q&A
2026-08-21
EPSS Evaluated
N/A
NVD
CVE-2026-77763
EUVD
EUVD-2026-63899

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
juicedata juicefs 1.4.1

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-22 The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Attack-Flow Graph

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Executive Summary

CVE-2026-77763 is a path traversal vulnerability in JuiceFS's filestore backend. It occurs because object keys are directly joined to the root path without validation, allowing keys with traversal segments like '../' to escape the intended storage directory. This affects operations such as Put, Get, Delete, and others that rely on the unchecked path.

Detection Guidance

To detect this vulnerability, check JuiceFS logs for sync operations involving untrusted sources. Look for paths containing '../' or similar traversal sequences in object keys. Verify if files were written outside the intended filestore root directory during sync operations.

Impact Analysis

If you sync files from an untrusted source like a shared or public bucket, an attacker could craft object keys to write files outside the intended directory. This could lead to unauthorized file creation, data corruption, or system compromise depending on the operations performed.

Compliance Impact

This vulnerability could lead to unauthorized file writes outside intended directories, potentially exposing sensitive data stored in JuiceFS. This may violate GDPR's data protection requirements for secure storage and access controls, and HIPAA's safeguards for protected health information if medical data is involved.

Mitigation Strategies

Upgrade JuiceFS to a patched version that includes the path traversal fix. Ensure all sync operations from untrusted sources are reviewed and restricted. Monitor file system writes to detect unauthorized access attempts.

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