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

Exp

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.

Published: 2023-12-05 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-49284 is rated Exploit Available (50/100): CVSS Low severity, with low exploitation likelihood (EPSS 0.47%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2023-49284

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2023-49284

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 0.47% +0.42%
2 2025-03-17 0.04% 0.06% +0.01%
3 2023-12-05 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-49284

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.9 3.1 LOW
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.3 2.5 [email protected]
6.6 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.3 5.2 [email protected]

Weakness enumeration for CVE-2023-49284

OS Trackers for CVE-2023-49284

vendor priority summary link
alpine — CVE-2023-49284: 1 source package rows (fish); 7 state rows across 7 repos (3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 7. https://security.alpinelinux.org/vuln/CVE-2023-49284
debian not yet assigned CVE-2023-49284 not yet assigned priority: Debian including 1 source packages (fish), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2023-49284
suse medium CVE-2023-49284 severity moderate: SUSE including 8 source package names (fish-3.3.1-bp154.3.3.1, fish-3.3.1-bp155.4.3.1, …), 12 product×package rows across 6 product lines (SUSE Linux Enterprise Server 16.0, SUSE Package Hub 15 SP4, … (6 product lines)): Fixed 12. https://www.suse.com/security/cve/CVE-2023-49284/
ubuntu medium CVE-2023-49284 medium priority: Ubuntu including 1 source packages (fish), 12 status rows across 12 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 7, ignored 5. https://ubuntu.com/security/CVE-2023-49284

Affected software / configurations for CVE-2023-49284

Vendor Product Version Raw CPE
fishshell fish < 3.6.2 cpe:2.3:a:fishshell:fish:*:*:*:*:*:*:*:*

References for CVE-2023-49284

cvelogic Threat Intelligence