Commvault Web Server: vulnerability flaw under attack

What is affected

Commvault Web Server is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

Commvault Web Server contains an unspecified vulnerability that allows a remote, authenticated attacker to create and execute webshells.

What an attacker can do

This is a vulnerability flaw. It lets an attacker misuse the product in a way its maker did not intend. CISA lists it because attackers are confirmed to be using it against real systems.

How it is reached

Over the internet or network

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Commvault Web Server at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• documentation.commvault.comdocumentation.commvault.com/securityadvisories/CV_2025_03_1.html
• commvault.comwww.commvault.com/blogs/notice-security-advisory-update

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on April 28, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 19, 2025, 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 2.5% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 84% of all scored vulnerabilities.

Its CVSS severity score is 8.7 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Commvault Web Server has an unspecified vulnerability that can be exploited by a remote, authenticated attacker. According to the Commvault advisory: "Webservers can be compromised through bad actors creating and executing webshells." Fixed in version 11.36.46, 11.32.89, 11.28.141, and 11.20.217 for Windows and Linux platforms. This vulnerability was added to the CISA Known Exploited Vulnerabilities (KEV) Catalog on 2025-04-28.