SSRF (Server-Side Request Forgery) in org.geysermc.geyser:core (CVE-2026-42188)
Summary
SSRF in org.geysermc.geyser:core (CVE-2026-42188). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.9.3 or later.
Original description
The description as published by the source.
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
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Setup Environment:
- Set up a Minecraft Server (Paper/Spigot) with the latest version of Geyser installed.
- Ensure you have a Bedrock client connected.
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Prepare Listener:
- Go to webhook.site and obtain a unique URL (e.g.,
https://webhook.site/YOUR-UUID).
- Go to webhook.site and obtain a unique URL (e.g.,
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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)
- Create a JSON payload pointing to your listener URL:
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Execute Command:
- Run t…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42188 has been found in org.geysermc.geyser:core.
Risk of unauthorized operations or information disclosure. CVSS score: 2.4/10.
What to do: upgrade org.geysermc.geyser:core to 2.9.3 or later.
If unsure, ask your IT team or search "org.geysermc.geyser:core CVE-2026-42188" on the vendor's site.
CVE-2026-42188 (org.geysermc.geyser:core) — CWE-918 / CVSS v3 2.4
Attack vector: remote (network-reachable)
Patched: 2.9.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in org.geysermc.geyser:core.
Check the vendor advisory for the affected versions of org.geysermc.geyser:core.
Severity: Low (CVSS 2.4/10). Risk of unauthorized operations or information disclosure.
Update to 2.9.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで org.geysermc.geyser:core を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade org.geysermc.geyser:core to 2.9.3ステージング環境で 2.9.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- exploit github.com
- package github.com
- web github.com