Executive brief
Emacs, a widely-used text editor, contains a flaw in its Flymake syntax checking mode that allows arbitrary code execution when editing untrusted files. An attacker can craft a malicious file that, when opened in Emacs with Flymake enabled, executes code with the privileges of the user running the editor. This poses a significant risk for developers and users who frequently work with files from untrusted sources.
Technical details
The vulnerability exists in Flymake mode when using language backends other than Lisp, where syntax checking operations execute arbitrary code embedded in the edited file. The attack is triggered passively when a user views or edits a malicious file in Emacs with Flymake enabled, requiring no additional user interaction beyond opening the file. An attacker gains code execution in the context of the user's Emacs process.
Affected products
- GNU Emacs prior to 31.2
Timeline
- 2026-09-23: disclosed