RARLAB UnRAR: file access flaw under attack

What is affected

RARLAB UnRAR is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

RARLAB UnRAR on Linux and UNIX contains a directory traversal vulnerability, allowing an attacker to write to files during an extract (unpack) operation.

What an attacker can do

This is a file access flaw. It lets an attacker read or write files they should never reach, such as configuration files that hold passwords, or upload a malicious file that the system then runs.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

CISA records this vulnerability as known to be used in ransomware campaigns: attackers use it to get in, then encrypt files and demand payment.

What to do

1. Update RARLAB UnRAR now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply updates per vendor instructions.

Vendor advisories and fixes

• rarlab.comwww.rarlab.com/rar/rarlinux-x32-612.tar.gz

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on August 9, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by August 30, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 99% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.9% of all scored vulnerabilities.

Its CVSS severity score is 7.5 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

RARLAB UnRAR before 6.12 on Linux and UNIX allows directory traversal to write to files during an extract (aka unpack) operation, as demonstrated by creating a ~/.ssh/authorized_keys file. NOTE: WinRAR and Android RAR are unaffected.