CVE-2014-6271: GNU Bourne-Again Shell (Bash) Arbitrary Code Execution Vulnerability

100

Patch now

CRITICAL 9.8EXPLOITEDREMOTEWATCHLISTUPGRADEUPGRADEMITIGATE

CVE-2014-6271 is a critical-severity flaw (CVSS 9.8) affecting bash, eos, linux, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Exploited in the wild (CISA KEV)
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	100.0% (top 1%)
CISA exploited list	Yes, fix due 2022-07-28
Weakness	CWE-78
Published	2014-09-24
Last modified	2026-06-17

Publisher (CNA): Debian GNU/Linux · Vendor: arista · gnu · mageia · oracle · qnap · redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2014-09-24 18:48 UTCPublished CVE record published
2022-01-28Exploited Added to the CISA Known Exploited Vulnerabilities list
2022-07-28Deadline CISA due date for US federal agencies to patch
2026-06-17 00:12 UTCUpdated Record last modified

gnu bash UPGRADE

Affected: <= 4.3

Fixed in: newer than 4.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bash || rpm -q bash || bash --version

2. UPGRADE to newer than 4.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bash

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bash

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

arista eos UPGRADE

Affected: >= 4.9.0 and < 4.9.12 · >= 4.10.0 and < 4.10.9 · >= 4.11.0 and < 4.11.11 · >= 4.12.0 and < 4.12.9 · >= 4.13.0 and < 4.13.9 · >= 4.14.0 and < 4.14.4f

Fixed in: 4.9.12, 4.10.9, 4.11.11, 4.12.9, 4.13.9, 4.14.4f

Safe to downgrade to: a release before 4.9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

oracle linux MITIGATE

Affected: 4 · 5 · 6

Fixed in: no fixed release known

Safe to downgrade to: a release before 4

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

qnap qts UPGRADE

Affected: < 4.1.1 · 4.1.1 · 4.1.1 build_0927

Fixed in: 4.1.1

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

mageia mageia MITIGATE

Affected: 3.0 · 4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat gluster storage server for on-premise DOWNGRADE

Affected: 2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1

1. Check installed version

apt-cache policy gluster-storage-server-for-on-premise || rpm -q gluster-storage-server-for-on-premise || gluster-storage-server-for-on-premise --version

2. No fixed release: DOWNGRADE to a release before 2.1 (Debian / Ubuntu)

apt-cache madison gluster-storage-server-for-on-premise sudo apt install gluster-storage-server-for-on-premise=<VERSION_BEFORE_2.1> sudo apt-mark hold gluster-storage-server-for-on-premise

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list gluster-storage-server-for-on-premise sudo dnf downgrade gluster-storage-server-for-on-premise-<VERSION_BEFORE_2.1> sudo dnf versionlock add gluster-storage-server-for-on-premise

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · perl-Net-IDN-Encode · FIXED · 2.600-1.fc46 · FEDORA-2026-84eff0ea64 · source

sudo dnf upgrade --advisory=FEDORA-2026-84eff0ea64

Fedora ELN · libXISF · FIXED · 0.2.15-2.eln159 · FEDORA-2026-b9e2d1bda0 · source

sudo dnf upgrade --advisory=FEDORA-2026-b9e2d1bda0

Debian 12 · bash · FIXED · 4.3-9.1

sudo apt update && sudo apt install --only-upgrade bash dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bash)" ge "4.3-9.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · bash · FIXED · 4.3-9.1

sudo apt update && sudo apt install --only-upgrade bash dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bash)" ge "4.3-9.1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 4 Extended Lifecycle Support · bash · FIXED · bash-3.0-27.el4.2

sudo dnf upgrade --advisory=RHSA-2014:1294 rpm -q bash

RHEL 5 · bash · FIXED · bash-3.2-33.el5.1

sudo dnf upgrade --advisory=RHSA-2014:1293 rpm -q bash

RHEL 5.6 Long Life · bash · FIXED · bash-3.2-24.el5_6.1

sudo dnf upgrade --advisory=RHSA-2014:1294 rpm -q bash

RHEL 5.9 Extended Update Support · bash · FIXED · bash-3.2-32.el5_9.2

sudo dnf upgrade --advisory=RHSA-2014:1294 rpm -q bash

RHEL 6 · bash · FIXED · bash-4.1.2-15.el6_5.1

sudo dnf upgrade --advisory=RHSA-2014:1293 rpm -q bash

Amazon Linux 1 · see advisory · FIXED · ALAS-2014-418 · source

sudo yum update --advisory=ALAS-2014-418

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: Advantech Switch - 'Shellshock' Bash Environment Variable Command Injection (Metasploit)
Exploit-DB: GNU Bash - Environment Variable Command Injection (Metasploit)
Exploit-DB: IPFire - 'Shellshock' Bash Environment Variable Command Injection (Metasploit)
Exploit-DB: Bash CGI - 'Shellshock' Remote Command Injection (Metasploit)
Exploit-DB: IPFire - CGI Web Interface (Authenticated) Bash Environment Variable Code Injection
Exploit-DB: QNAP - Admin Shell via Bash Environment Variable Code Injection (Metasploit)
Exploit-DB: QNAP - Web Server Remote Code Execution via Bash Environment Variable Code Injection (Metasploit)
Exploit-DB: TrendMicro InterScan Web Security Virtual Appliance - 'Shellshock' Remote Command Injection

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2014-6271?

bash: upgrade to newer than 4.3; eos: upgrade to 4.9.12, 4.10.9, 4.11.11, 4.12.9, 4.13.9, 4.14.4f; linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2014-6271 being exploited?

Yes. CVE-2014-6271 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2014-6271 affect?

CVE-2014-6271 affects bash, eos, linux. Severity is critical (CVSS 9.8). 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 F

How urgent is CVE-2014-6271?

Priority 100/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSH vulnerabilities · Apache HTTP Server vulnerabilities · QNAP vulnerabilities

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References

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