Canadian Cyber Centre Warns of Active Roundcube Webmail Code Injection Attacks

Key points

• Roundcube Webmail is being actively targeted through a code injection flaw.
• Canadian Cyber Centre is flagging the issue as high severity.
• No CVE identifier has been assigned in the available facts.
• Apply the vendor patch immediately; scale of compromise remains unknown.

In May, attackers began exploiting a vulnerability in Roundcube Webmail that allows code injection. The Canadian Cyber Centre has drawn attention to the issue, rating it high severity. No CVE identifier has been published in the information available, and the number of affected organizations has not been disclosed.

Roundcube Webmail is widely used by universities, businesses, and public-sector bodies to provide browser-based email access. Any school district, municipality, or provincial service running an unpatched instance could be exposed. Because the flaw enables code injection, a successful attack may go beyond mailbox access and affect the underlying web server.

Active exploitation raises the stakes. Attackers do not need to wait for defenders to discover the issue; they are already using it. Code injection can let an intruder run unauthorized commands, alter application behavior, or establish persistence. For K-12 and government environments, that could mean disrupted communications, data exposure, or a foothold for broader network compromise.

The absence of a CVE does not make the threat less urgent. It may simply reflect that tracking details are still being coordinated. Administrators should watch for vendor updates, Canadian Cyber Centre guidance, and signs of exploitation such as unexpected files, modified scripts, or unusual outbound traffic. Until the patch is applied, limiting exposure and increasing monitoring are the best immediate defenses.

What to do now

1. Inventory every Roundcube Webmail instance, including forgotten test, staging, and departmental deployments.
2. Apply the vendor's patch immediately; if no patch is available, take the service offline or restrict it to trusted networks.
3. Review web server and application logs for code injection attempts, unexpected PHP files, and modified Roundcube files.
4. Rotate credentials, session secrets, and API keys used by the mail service if compromise is suspected.
5. Enable enhanced monitoring and alerting for unusual outbound connections, new administrative accounts, or persistence mechanisms.
6. Report suspected incidents to the Canadian Cyber Centre and follow their guidance.
7. Communicate with users about phishing and suspicious email activity while remediation is underway.

Original source

BleepingComputer