Sophos SFOS: sql injection flaw under attack

What is affected

Sophos SFOS 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.

Sophos Firewall operating system (SFOS) firmware contains a SQL injection vulnerability when configured with either the administration (HTTPS) service or the User Portal is exposed on the WAN zone. Successful exploitation may cause remote code execution to exfiltrate usernames and hashed passwords for the local device admin(s), portal admins, and user accounts used for remote access (but not external Active Directory or LDAP passwords).

What an attacker can do

This is a sql injection flaw. It lets an attacker read, change or delete records in the product's database. That often includes user accounts and stored passwords.

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 Sophos SFOS 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 updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on November 3, 2021, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 3, 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 42% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99% 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

A SQL injection issue was found in SFOS 17.0, 17.1, 17.5, and 18.0 before 2020-04-25 on Sophos XG Firewall devices, as exploited in the wild in April 2020. This affected devices configured with either the administration (HTTPS) service or the User Portal exposed on the WAN zone. A successful attack may have caused remote code execution that exfiltrated usernames and hashed passwords for the local device admin(s), portal admins, and user accounts used for remote access (but not external Active Directory or LDAP passwords)