Rejetto HTTP File Server: vulnerability flaw under attack

What is affected

Rejetto HTTP File 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.

Rejetto HTTP File Server contains an improper neutralization of special elements used in a template engine vulnerability. This allows a remote, unauthenticated attacker to execute commands on the affected system by sending a specially crafted HTTP request.

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

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. 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 Rejetto HTTP File 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 or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• github.comgithub.com/rejetto/hfs?tab=readme-ov-file#installation
• rejetto.comwww.rejetto.com/hfs/

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on July 9, 2024, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by July 30, 2024, 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 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

Rejetto HTTP File Server, up to and including version 2.3m, is vulnerable to a template injection vulnerability. This vulnerability allows a remote, unauthenticated attacker to execute arbitrary commands on the affected system by sending a specially crafted HTTP request. As of the CVE assignment date, Rejetto HFS 2.3m is no longer supported.