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
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| transmission | transmission | 4.0.0 – < 4.1.3 | 4.1.3 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | transmission | 4.1.3+dfsg-1 | — |
| Debian 13 | transmission | No fix yet | — |
| Debian 12 | transmission | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | transmission | No fix yet | — |
| Ubuntu 26.04 LTS | transmission | No fix yet | — |
| Ubuntu 24.04 LTS | transmission | No fix yet | — |
| Ubuntu 22.04 LTS | transmission | No fix yet | — |
| Ubuntu 20.04 LTS | transmission | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | transmission | No fix yet | — |
| Ubuntu 16.04 LTS | transmission | No fix yet | — |
Automated scanner template
A ready-made Nuclei template detects this vulnerability automatically. Vulnerabilities with public scanner templates are typically probed across the internet soon after the template appears — exposed systems should be patched first.
- Transmission 4.0.0-4.1.2 - Permissive CORS Exposes RPC Session ID http/cves/2026/CVE-2026-116748.yaml
Source: projectdiscovery/nuclei-templates (MIT) — updated daily. Only links are listed.
References
- Pull Request #8938 issue-tracking patch
- Patch Commit patch
- https://github.com/transmission/transmission product
- transmission 4.1.3 Release Notes release-notes
- https://github.com/transmission/transmission/blob/4.1.2/libtransmission/rpc-server.cc#L560 technical-description
- https://joshua.hu/transmission-cors-rpc-csrf-rce-drive-by-exploit third-party-advisory
- VulnCheck Advisory: Transmission 4.0.0 before 4.1.3 Permissive CORS Leaks RPC Anti-CSRF Token third-party-advisory