CVE-2026-43910

Appium Java Client is the Java language binding for writing Appium tests that conform to the W3C WebDriver protocol. From 8.2.1 until 10.1.1, when directConnect(true) is enabled, AppiumCommandExecutor.setDirectConnect() reads the directConnectHost, directConnectPort, and directConnectPath fields from the server's NEW_SESSION response and rebuilds the client's server URL from them, validating only that the protocol is https, with no host allowlist or IP validation; a rogue or compromised server can therefore redirect all subsequent session traffic to an arbitrary destination, enabling full interception of session traffic and a server-side request forgery pivot to internal hosts, including cloud metadata (IMDS) credential theft. This vulnerability is fixed in 10.1.1.

Appium Java Client is the Java language binding for writing Appium tests that conform to the W3C WebDriver protocol. From 8.2.1 until 10.1.1, when directConnect(true) is enabled, AppiumCommandExecutor.setDirectConnect() reads the directConnectHost, directConnectPort, and directConnectPath fields from the server's NEW_SESSION response and rebuilds the client's server URL from them, validating only that the protocol is https, with no host allowlist or IP validation; a rogue or compromised server can therefore redirect all subsequent session traffic to an arbitrary destination, enabling full interception of session traffic and a server-side request forgery pivot to internal hosts, including cloud metadata (IMDS) credential theft. This vulnerability is fixed in 10.1.1.

Summary

When directConnect(true) is enabled, appium/java-client unconditionally accepts directConnectHost, directConnectPort, and directConnectPath from the server's NEW_SESSION response and silently redirects all subsequent session traffic to the attacker-specified endpoint — with no allowlist, no host validation, and no user notification.

Affected Code

• AppiumCommandExecutor.java (line 196–219): setDirectConnect() builds a new URL from server-supplied fields and calls overrideServerUrl(newUrl) without validating host/IP.
• DirectConnect.java: getUrl() constructs protocol://host:port/path with no allowlist.

Root Cause

Only the protocol is validated (must equal "https"). The destination host and port are never checked against any allowlist or denylist.

PoC (confirmed)

A rogue server injecting directConnectHost=127.0.0.1:4443 causes the client to silently redirect all post-session commands:

[bootstrap] POST /wd/hub/session [bootstrap] Injecting directConnect -> https://127.0.0.1:4443/wd/hub [redirect-target] HIT #1: GET /wd/hub/session/poc-session-001/source [redirect-target] HIT #2: DELETE /wd/hub/session/poc-session-001

Original source code unmodified — confirmed via git diff HEAD (empty).

Evidence Screenshots

Screenshot 1 — Rogue server capturing redirected traffic:

<img width="887" height="146" alt="1" src="https://github.com/user-attachments/assets/cc28002c-ea20-4ac8-8336-cec632e3c842" />

Screenshot 2 — Java client processing response from attacker host:

<img width="788" height="130" alt="2" src="https://github.com/user-attachments/assets/222cbab0-0d53-45b2-847d-6aa4e3b79370" />

Impact

• Full interception of session traffic
• Network pivot to internal hosts (RFC-1918, 169.254.169.254)
• Cloud credential theft via IMDS endpoint
• Escalates to ~8.1 High in CI/CD environments where directConnect(true) is set in shared base configuration

Suggested Fix

Add allowlist validation before overrideServerUrl() is called, and/or block RFC-1918/loopback/link-local destinations by default.

poc_appium_directconnect.zip

Appium Java Client is the Java language binding for writing Appium tests that conform to the W3C WebDriver protocol. From 8.2.1 until 10.1.1, when directConnect(true) is enabled, AppiumCommandExecutor.setDirectConnect() reads the directConnectHost, directConnectPort, and directConnectPath fields from the server's NEW_SESSION response and rebuilds the client's server URL from them, validating only that the protocol is https, with no host allowlist or IP validation; a rogue or compromised server can therefore redirect all subsequent session traffic to an arbitrary destination, enabling full interception of session traffic and a server-side request forgery pivot to internal hosts, including cloud metadata (IMDS) credential theft. This vulnerability is fixed in 10.1.1.

Appium Java Client is the Java language binding for writing Appium tests that conform to the W3C WebDriver protocol. From 8.2.1 until 10.1.1, when directConnect(true) is enabled, AppiumCommandExecutor.setDirectConnect() reads the directConnectHost, directConnectPort, and directConnectPath fields from the server's NEW_SESSION response and rebuilds the client's server URL from them, validating only that the protocol is https, with no host allowlist or IP validation; a rogue or compromised server can therefore redirect all subsequent session traffic to an arbitrary destination, enabling full interception of session traffic and a server-side request forgery pivot to internal hosts, including cloud metadata (IMDS) credential theft. This vulnerability is fixed in 10.1.1.

Summary

When directConnect(true) is enabled, appium/java-client unconditionally accepts directConnectHost, directConnectPort, and directConnectPath from the server's NEW_SESSION response and silently redirects all subsequent session traffic to the attacker-specified endpoint — with no allowlist, no host validation, and no user notification.

Affected Code

• AppiumCommandExecutor.java (line 196–219): setDirectConnect() builds a new URL from server-supplied fields and calls overrideServerUrl(newUrl) without validating host/IP.
• DirectConnect.java: getUrl() constructs protocol://host:port/path with no allowlist.

Root Cause

Only the protocol is validated (must equal "https"). The destination host and port are never checked against any allowlist or denylist.

PoC (confirmed)

A rogue server injecting directConnectHost=127.0.0.1:4443 causes the client to silently redirect all post-session commands:

[bootstrap] POST /wd/hub/session [bootstrap] Injecting directConnect -> https://127.0.0.1:4443/wd/hub [redirect-target] HIT #1: GET /wd/hub/session/poc-session-001/source [redirect-target] HIT #2: DELETE /wd/hub/session/poc-session-001

Original source code unmodified — confirmed via git diff HEAD (empty).

Evidence Screenshots

Screenshot 1 — Rogue server capturing redirected traffic:

<img width="887" height="146" alt="1" src="https://github.com/user-attachments/assets/cc28002c-ea20-4ac8-8336-cec632e3c842" />

Screenshot 2 — Java client processing response from attacker host:

<img width="788" height="130" alt="2" src="https://github.com/user-attachments/assets/222cbab0-0d53-45b2-847d-6aa4e3b79370" />

Impact

• Full interception of session traffic
• Network pivot to internal hosts (RFC-1918, 169.254.169.254)
• Cloud credential theft via IMDS endpoint
• Escalates to ~8.1 High in CI/CD environments where directConnect(true) is set in shared base configuration

Suggested Fix

Add allowlist validation before overrideServerUrl() is called, and/or block RFC-1918/loopback/link-local destinations by default.

poc_appium_directconnect.zip