Cloudreve: Path Traversal in WOPI PUT_RELATIVE Allows Arbitrary File Creation in Owner Account

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-55495: 0.38% estimated exploitation activity in the next 30 days; percentile 31.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Cloudreve's WOPI PUTRELATIVE handler treats X-WOPI-SuggestedTarget as a path, not a filename. It splits the header on / and joins the segments onto the source file's directory with URI.JoinRaw, which feeds Go's url.JoinPath. url.JoinPath resolves ./.. segments, so a slash-bearing target such as a/../../evil.docx collapses to a location outside the source file's directory. The lower-level upload path then validates only the final, already-cleaned basename (evil.docx), which is harmless, and checks ownership against the resolved ancestor — which is still the same user's drive. A WOPI access token is bound to exactly one file (the route enforces fileId == session.FileID with a 403 otherwise). PUTRELATIVE escapes that per-file scope: a token issued for one file can create (and, conditionally, overwrite) files elsewhere in the same account. Root cause (verified at 26b6b10) 1. Token is single-file scoped (the boundary being escaped) — middleware ViewerSessionValidation: Route: wopi…

Published by the source

18 Aug 2026, 14:32 UTC

Last modified by the source

18 Aug 2026, 15:00 UTC

Source last checked

26 Oct 2026, 15:27 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-49h3-cwhj-4737

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-6097

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# Patch Next advisory brief: CVE-2026-55495

Advisory: Cloudreve: Path Traversal in WOPI PUT_RELATIVE Allows Arbitrary File Creation in Owner Account
IDs: CVE-2026-55495, GHSA-49h3-cwhj-4737
Record: https://patchnext.com/advisories/cve-2026-55495 (revision 2, source checked 26 Oct 2026, 15:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/cloudreve/Cloudreve/v4 4.0.0-20260613023150-7968e50429ef. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/cloudreve/Cloudreve/v3: affected <= 3.0.0-20250225100611-da4e44b77af4
- Go github.com/cloudreve/Cloudreve: affected every version
- Go github.com/cloudreve/Cloudreve/v4: affected < 4.0.0-20260613023150-7968e50429ef; fixed in 4.0.0-20260613023150-7968e50429ef

## Suggested inspection (read-only)
- Go github.com/cloudreve/Cloudreve/v3: check the installed version with your package manager.
- Go github.com/cloudreve/Cloudreve: check the installed version with your package manager.
- Go github.com/cloudreve/Cloudreve/v4: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/cloudreve/Cloudreve/v3, github.com/cloudreve/Cloudreve, github.com/cloudreve/Cloudreve/v4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6097 (OSV record GO-2026-6097 lists affected ranges: Go github.com/cloudreve/Cloudreve >=0; Go github.com/cloudreve/Cloudreve/v3 >=0; Go github.com/cloudreve/Cloudreve/v4 >=0 <4.0.0-20260613023150-7968e50429ef (fixed))
- Verified: https://github.com/advisories/GHSA-49h3-cwhj-4737 (GitHub-reviewed advisory GHSA-49h3-cwhj-4737 lists affected ranges: Go github.com/cloudreve/Cloudreve/v4 >=0 =0 <=3.0.0-20250225100611-da4e44b77af4)

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