CVE-2021-40153: squashfs_opendir in unsquash-1.c in Squashfs-Tools 4.5 stores the filename in the directory entry; this is the
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HIGH 8.1WATCHLISTDOWNGRADEMITIGATEMITIGATE
CVE-2021-40153 is a high-severity flaw (CVSS 8.1) affecting squashfs-tools, fedora, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
squashfs_opendir in unsquash-1.c in Squashfs-Tools 4.5 stores the filename in the directory entry; this is then used by unsquashfs to create the new file during the unsquash. The filename is not validated for traversal outside of the destination directory, and thus allows writing to locations outside of the destination.
Why this priority
High severity
Public exploit reference
On your watchlist
No fix is published yet: follow the downgrade or mitigation steps.
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.
fedoraproject fedora MITIGATE
Affected: 34 · 33
Fixed in: no fixed release known
Safe to downgrade to: a release before 33
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.
debian debian linux MITIGATE
Affected: 9.0 · 10.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 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.
redhat enterprise linux MITIGATE
Affected: 7.0 · 8.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.0
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.
Verify at the official sourceNVD · 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.
Quick answers
How do I fix CVE-2021-40153?
squashfs-tools: downgrade or apply the listed mitigation; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-40153 being exploited?
CVE-2021-40153 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-2021-40153 affect?
CVE-2021-40153 affects squashfs-tools, fedora, debian linux. Severity is high (CVSS 8.1). squashfs_opendir in unsquash-1.c in Squashfs-Tools 4.5 stores the filename in the directory entry; this is then used by unsquashfs to create the new file during the unsquash. The filename is not validated for traversal outside of the destin
How urgent is CVE-2021-40153?
Priority 60/100. High severity; Public exploit reference; On your watchlist
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