PatchTheCVECVE-2016-9401: popd in bash might allow local users to bypass the restricted shell and cause a use-after-free via a crafted a
33
Routine
MEDIUM 5.5WATCHLISTUPGRADEMITIGATEMITIGATE
CVE-2016-9401 is a medium-severity flaw (CVSS 5.5) affecting bash, debian linux, enterprise linux desktop. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
popd in bash might allow local users to bypass the restricted shell and cause a use-after-free via a crafted address.
Why this priority
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.5 (Medium) |
| Attack vector | Local |
| Attack complexity | Low |
| Privileges needed | Low |
| User interaction | None |
| EPSS exploit chance | 0.4% (top 64%) |
| CISA exploited list | No |
| Weakness | CWE-416 |
| Published | 2017-01-23 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
gnu bash UPGRADE
Affected: < 4.4 · 4.4 patch1 · 4.4 patch2 · 4.4 patch3 · 4.4 patch4 · 4.4 patch5
Fixed in: 4.4
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy bash || rpm -q bash || bash --version
2. UPGRADE to 4.4 (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.
debian debian linux MITIGATE
Affected: 8.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 8.0
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 enterprise linux desktop MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
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 enterprise linux server MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
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 enterprise linux server aus MITIGATE
Affected: 7.4 · 7.6 · 7.7
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.4
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.
redhat enterprise linux server eus MITIGATE
Affected: 7.4 · 7.5 · 7.6 · 7.7
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.4
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.
Verify at the official source NVD · CVE Program · 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.
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-2016-9401?
bash: upgrade to 4.4; debian linux: mitigate or apply the listed mitigation; enterprise linux desktop: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2016-9401 being exploited?
CVE-2016-9401 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2016-9401 affect?
CVE-2016-9401 affects bash, debian linux, enterprise linux desktop. Severity is medium (CVSS 5.5). popd in bash might allow local users to bypass the restricted shell and cause a use-after-free via a crafted address.
How urgent is CVE-2016-9401?
Priority 33/100. On your watchlist
Software pages
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