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High, CVSS 7.5

Yamcs has Unauthenticated Directory Traversal

CVE-2026-55552GHSA-9jg3-g3wh-w9pj

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (org.yamcs:yamcs-core 5.12.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS
  • CVE-2026-55552: 1.72% estimated exploitation activity in the next 30 days; percentile 77.52 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Attack type: Unauthenticated remote

Impact: Attackers can access any system files from the underlying host.

Affected components: HttpRequestHandler.java, StaticFileHandler.java An Unauthenticated Directory Traversal vulnerability exists in Yamcs

Steps to Reproduce: 1. Start Yamcs and login as a user 2. Paste the following URL in the browser and press enter: ``` http://localhost:8090//etc/passwd ``` 3. The `/etc/passwd` file will be downloaded.

Acknowledgements This vulnerability was discovered by Abderrahim Dahmani while solving a STARPWN 2025 CTF challenge at DEFCON 33 offered by VisionSpace Technologies.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from osv record GHSA-9jg3-g3wh-w9pj

Agent brief

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# Patch Next advisory brief: CVE-2026-55552

Advisory: Yamcs has Unauthenticated Directory Traversal
IDs: CVE-2026-55552, GHSA-9jg3-g3wh-w9pj
Record: https://patchnext.com/advisories/cve-2026-55552 (revision 1, source checked 23 Oct 2026, 22:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.yamcs:yamcs-core 5.12.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.yamcs:yamcs-core: affected < 5.12.0; fixed in 5.12.0

## Suggested inspection (read-only)
- Maven org.yamcs:yamcs-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.yamcs:yamcs-core.
- 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/GHSA-9jg3-g3wh-w9pj (OSV record GHSA-9jg3-g3wh-w9pj lists affected ranges: Maven org.yamcs:yamcs-core >=0 <5.12.0 (fixed))

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