What’s Vulnerable › Vulnerabilities

CVE-2026-116748: Transmission 4.0.0 before 4.1.3 Permissive CORS Leaks RPC Anti-CSRF Token

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-10-26 · updated 2026-10-31
• Weakness: CWE-942

Description

Transmission 4.0.0 before 4.1.3 contains a permissive CORS vulnerability in handle_request() in rpc-server.cc that exposes the X-Transmission-Session-Id anti-CSRF token to any web origin. Malicious web pages can read the token from the 409 handshake response and replay it to issue RPC calls, enabling script-torrent-done execution, download-dir changes, or torrent and data deletion.

Affected products

• transmission: from 4.0.0 before 4.1.3 — fixed in 4.1.3

How to fix

Upgrade to a fixed version: transmission 4.1.3. Check the vendor advisory for mitigations.

References

• https://github.com/transmission/transmission
• https://github.com/transmission/transmission/blob/4.1.2/libtransmission/rpc-server.cc#L560
• https://github.com/transmission/transmission/commit/c6a1bd2017a0fea9c956737c213f23e4b0f7929e
• https://github.com/transmission/transmission/pull/8938
• https://github.com/transmission/transmission/releases/tag/4.1.3
• https://joshua.hu/transmission-cors-rpc-csrf-rce-drive-by-exploit
• https://www.vulncheck.com/advisories/transmission-4.0.0-before-4.1.3-permissive-cors-leaks-rpc-anti-csrf-token

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