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The vulnerability involves the injection of ANSI escape sequences into the terminal output of Composer commands. ANSI sequences are control characters that instruct terminals to perform actions like cursor movement, color changes, or screen clearing. When Composer downloads from remote sources, such as package repositories, if an attacker controls those sources, they can embed malicious ANSI sequences in the output. Composer, in affected versions, does not sanitize or filter these sequences before displaying them to the user’s terminal. As a result, when commands like `composer require` or `composer update` execute, the terminal interprets the injected sequences. This can cause the output to become garbled, overwritten, or entirely cleared, disrupting the user’s view. In severe cases, repeated or specific sequences could freeze or crash the terminal application, leading to a denial-of-service. The vulnerability exploits the trust in remote source output and the terminal’s inherent interpretation of ANSI codes. It is considered low severity because it primarily affects display integrity rather than system security, and no proven exploit exists. However, it highlights a lack of output sanitization in Composer’s handling of remote content.
Platform: Composer
Version: v2.0.0-2.2.25 v2.3.0-2.9.2
Vulnerability: ANSI sequence injection
Severity: Low
date: Dec 30 2025
Prediction: Patched Dec 30
What Undercode Say:
Showing bash commands and codes related to the blog
Example ANSI injection
echo -e “\033[2J\033[H”
Simulating malicious output
printf “\033[31mFake error\033[0m\n”
Check Composer version
composer –version
Update to patched version
composer self-update –2.2.26
how Exploit:
Attacker controls remote source. Embeds ANSI sequences in package metadata or scripts. User runs Composer command. Terminal interprets sequences. Output mangled or terminal DoS.
Protection from this CVE
Upgrade to patched versions. Use composer self-update. Avoid untrusted sources.
Impact:
Mangled terminal output. Confusion for users. Potential terminal DoS.
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Sources:
Reported By: github.com
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