---
id: "CVE-2014-6271"
kind: "vulnerability"
aliases: ["CVE-2014-6271"]
title: "GNU Bourne-Again Shell (Bash): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution Vulnerability"
severity: "critical"
cvss: 10.0
epss: 0.99999
exploited: true
status: "open"
category: "runtime"
products: [{"name": "GNU Bourne-Again Shell (Bash)", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["bash", "cgi", "exploited", "linux", "macos", "runtime", "self-hosted"]
not_affected_if: ["no-bash-in-request-path", "patched-bash"]
published_at: "2014-09-24T18:48:04+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2014-6271", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2014-6271", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2014-6271", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# GNU Bourne-Again Shell (Bash): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution Vulnerability

GNU Bash through 4.3 runs trailing code after function definitions in environment variable values, the Shellshock flaw. A remote attacker can execute commands on a system whose Bash reads attacker-controlled environment variables.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:GNU Bourne-Again Shell (Bash) affected ? fixed ?

## How to check

Run: bash -c 'env x="() { :;}; echo VULNERABLE" bash -c "echo test"' and see if VULNERABLE prints.
Check the Bash version with: bash --version (4.3 and earlier are affected).

## Fix

Update Bash to a patched release from your OS vendor and confirm the test above no longer prints VULNERABLE.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2014-6271
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2014-6271
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2014-6271

## From the sources

GNU Bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code via a crafted environment, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution, aka "ShellShock."  NOTE: the original fix for this issue was incorrect; CVE-2014-7169 has been assigned to cover the vulnerability that is still present after the incorrect fix.

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