CVE-2023-49284 Command substitution output can trigger shell expansion in fish shell

Low 3.9 Published 4 Dec 2023 Updated 13 Feb 2025

Attackers can trigger shell expansion via command substitution output, potentially causing denial of service or information disclosure in fish shell.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2023-49284?

CVE-2023-49284 is a low-severity vulnerability in fish-shell, published on 4 Dec 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

fish is a smart and user-friendly command line shell for macOS, Linux, and the rest of the family. fish shell uses certain Unicode non-characters internally for marking wildcards and expansions. It will incorrectly allow these markers to be read on command substitution output, rather than transforming them into a safe internal representation. While this may cause unexpected behavior with direct input (for example, echo \UFDD2HOME has the same output as echo $HOME), this may become a minor security problem if the output is being fed from an external program into a command substitution where this output may not be expected. This design flaw was introduced in very early versions of fish, predating the version control system, and is thought to be present in every version of fish released in the last 15 years or more, although with different characters. Code execution does not appear to be possible, but denial of service (through large brace expansion) or information disclosure (such as variable expansion) is potentially possible under certain circumstances. fish shell 3.6.2 has been released to correct this issue. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Weakness: CWE-436

Which versions are affected by CVE-2023-49284?

It affects 1 product.

Linux distribution packages (5)

`fish` SUSE:Package Hub 15 SP4	All versions	`3.3.1-bp154.3.3.1`
`fish` SUSE:Package Hub 15 SP5	All versions	`3.3.1-bp155.4.3.1`
`fish` openSUSE:Leap 15.4	All versions	`3.3.1-bp154.3.3.1`
`fish` openSUSE:Leap 15.5	All versions	`3.3.1-bp155.4.3.1`
`fish` openSUSE:Tumbleweed	All versions	`3.6.4-1.1`

Products include Fishshell Fish.

How do I fix CVE-2023-49284?

Upgrade to a fixed version.

Is CVE-2023-49284 being exploited?

There is no known exploitation of CVE-2023-49284 in the wild and no public exploit code.

Sources

Also known as AZL-32081, DEBIAN-CVE-2023-49284, GHSA-2j9r-pm96-wp4f, MGASA-2023-0344, OESA-2023-1933, OESA-2023-1938 and 8 more.