CVE-2026-49864: wetty vulnerable to DOM XSS via file-download filename

Severity: high (CVSS 8.6 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-13 · updated 2026-09-09
Weakness: CWE-79

Description

wetty provides terminal access in browser over http/https. Prior to version 3.0.4, the wetty client decodes a base64 filename from the file-download escape sequence and interpolates it raw into a Toastify HTML string (`escapeMarkup: false`). Any output the victim renders - a `cat`'d file, a tailed log, an SSH MOTD, a `curl` response - that contains `\x1b[5i...:...\x1b[4i` runs script in the wetty origin and types attacker-chosen keystrokes into the victim's SSH session. Version 3.0.4 fixes the issue.

Affected products

butlerx wetty: before 3.0.4

References

https://github.com/butlerx/wetty/security/advisories/GHSA-p26j-h7wj-r568
https://github.com/butlerx/wetty/security/advisories/GHSA-p26j-h7wj-r568

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