Uncapped length of skin data fields submitted by players

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:N/I:N/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact Some skin data fields (e.g. skinID, geometryName) are not capped in length. These fields are typically saved in the NBT data of a player when the player quits the server, or during an autosave. This is problematic due to the 32767 byte limit on TAGStrings. If any of these fields exceeds 32767 bytes, an exception will be thrown during data saving, which will cause the server to crash. Other fields (such as skinGeometryData) are also uncapped, but those have a much larger 2 GB length limit, so this is not a concern for those, particularly considering the decompressed packet size limit of 2 MB. Patches PM3: 958a9dbf0fe3131ab60319c5a939f5dfbfe5dfbb PM4: 6492cac5c10f9fa8443ceddd2191a7b65b73f601 Workarounds A plugin may check player skins during PlayerLoginEvent and PlayerSkinChangeEvent and ensure that the offending fields are not larger than 32767 bytes. For more information If you have any questions or comments about this advisory: Email us at team@pmmp.io

Published by the source

6 Jan 2022, 23:53 UTC

Last modified by the source

11 Jan 2023, 05:03 UTC

Source last checked

26 Oct 2026, 13:56 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c6fg-99pr-25m9

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# Patch Next advisory brief: GHSA-c6fg-99pr-25m9

Advisory: Uncapped length of skin data fields submitted by players
IDs: GHSA-c6fg-99pr-25m9
Record: https://patchnext.com/advisories/ghsa-c6fg-99pr-25m9 (revision 1, source checked 26 Oct 2026, 13:56 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: pocketmine/pocketmine-mp 4.0.5, 3.26.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist pocketmine/pocketmine-mp: affected < 3.26.5; >= 4.0.0, < 4.0.5; fixed in 3.26.5, 4.0.5

## Suggested inspection (read-only)
- Packagist pocketmine/pocketmine-mp: 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 pocketmine/pocketmine-mp.
- 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://github.com/advisories/GHSA-c6fg-99pr-25m9 (GitHub-reviewed advisory GHSA-c6fg-99pr-25m9 lists affected ranges: Packagist pocketmine/pocketmine-mp >=0 =4.0.0 <4.0.5)

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