Ghostty released version 1.4.0 on October 27, 2026, fixing security flaws in how the terminal handles output and pasted text. For developers opening unfamiliar files or connecting to remote machines, several fixes matter before any speed improvements: malicious output could crash the terminal, and some graphics commands could make it read or delete unintended local files in limited circumstances. The release notes distinguish those risks from attacks that require a paste or click.
The graphics and paste advisories identify versions through 1.3.1 as affected and 1.4.0 as patched. This report follows the maintainers' disclosures; MrKeyoor hasn't reproduced the vulnerabilities or tested the updated app.
Output can trigger a flaw without a paste
The Kitty graphics advisory describes several validation and resource-management problems. A small crafted PNG could cause a multi-gigabyte allocation before rejection. Temporary-file checks also treated a path beginning with /tmpX as though it were inside /tmp, allowing a graphics transmission to read and unlink a file outside the permitted directories.
The attacker still needs the terminal to display malicious output. The advisory gives examples including a malicious program, a crafted file or an attacker-controlled remote host. Ghostty processes the graphics commands without prompting. That's why reviewing a command before running it doesn't, by itself, address this class of flaw: the output is another input to the terminal.
A separate tmux control-mode advisory affects Ghostty 1.3.0 and 1.3.1. A malicious byte stream could report an invalid scroll region and cause a crash that closes every window, tab and split in the Ghostty process. It doesn't require tmux to be installed.
The maintainers say no confidentiality or integrity impact has been demonstrated for that tmux flaw. They also note that it doesn't reproduce on every attempt because release builds encounter undefined behavior. Those limits distinguish the reported crash from a demonstrated theft or modification of data. Both advisories identify 1.4.0 as the fix.
The paste bypass depends on the receiving program
The paste-protection advisory concerns carriage returns, an invisible character that can act as Enter. Ghostty's safety check didn't recognize them as line endings, so pasted text could execute a command without the expected confirmation.
This affects programs outside bracketed paste mode, a mechanism that identifies pasted input to the receiving application. Interactive Bash, Zsh and Fish enable bracketed paste by default and aren't affected by this flaw, according to the advisory. Programs such as sh, along with password prompts from sudo or ssh, are affected. The attack requires someone to copy and paste malicious text.
Version 1.4.0 treats carriage returns like newlines: outside bracketed paste, either character requires confirmation. The advisory says affected versions have no configuration setting that prevents the problem. Manually inspecting clipboard contents is its stated precaution until updating.
Check the GTK requirements before upgrading
The release's system requirements keep macOS 13 as the minimum Mac version, but raise the GTK application requirements to GTK 4.18 and libadwaita 1.7. Ubuntu 24.04 LTS doesn't meet those requirements. The maintainers identify Flatpak as an option for systems with older libraries.
For those systems, the next check is whether the chosen package route supplies 1.4.0 with its required libraries. Staying on an older Ghostty version resolves the library mismatch but leaves the disclosed security fixes unapplied. The release notes also flag a change worth checking after installation: on macOS, selecting text no longer copies it by default. Set copy-on-select = primary if you need the previous selection behavior.