A patch for the vulnerability, which has been exploited since October 2022, had been issued by Barracuda last month to stop the exploit from allowing ESG backdooring. Credit: Barracuda Enterprise security company Barracuda has warned its customers against using email security gateway (ESG) appliances impacted by a recently disclosed zero-day exploit and to replace them immediately.A patch for the vulnerability, which has been exploited since October 2022, had been issued by Barracuda last month to stop the exploit from allowing ESG backdooring.“The vulnerability existed in a module which initially screens the attachments of incoming emails,” the company had said previously. “No other Barracuda products, including our SaaS email security services, were subject to the vulnerability identified.”Users whose appliances Barracuda believed were impacted are being notified via the ESG user interface of actions to take. Barracuda has also reached out to these specific customers. Replacement advised despite patchesThe vulnerability, dubbed CVE-2023-2868, was identified on May 19, 2023, and reportedly affected versions 5.1.3.001 through 9.2.0.006, allowing a remote attacker to achieve code execution on susceptible installations.Consequently, Barracuda released patches on May 20 and May 21 for all ESG appliances worldwide. In the latest update on the incident, however, the company has advised to replace the appliance irrespective of their patch status. “Impacted ESG appliances must be immediately replaced regardless of patch version level,” the company said in an update, adding that its “remediation recommendation at this time is a full replacement of the impacted ESG.”Multistrained malware usedThree different malware strains have been discovered to date on a subset of appliances allowing for persistent backdoor access, according to the company. Evidence of data exfiltration was identified on a subset of impacted appliances, the company said in a previous update.The different strains used — Saltwater, Seaspy, and Seaside — were all backdoor modules affecting data exfiltration. While both Saltwater and Seaside help establish a hack for the Barracuda SMTP daemon (bsmtpd) equipped to upload and download arbitrary files, execute commands, and tunnel malicious traffic, Seasspy is an x64 executable and linkable format (ELF) backdoor offering persistence capabilities, activated through a magic (remote, wake-on-LAN) packet.Mandiant, the Google-owned cybersecurity intelligence firm investigating the incident, has revealed source code overlaps between SEASPY and an open source backdoor called cd00r. Attacks have not been attributed to any known threat actor or group. Related content news UK government plans 2,500 new tech recruits by 2025 with focus on cybersecurity New apprenticeships and talent programmes will support recruitment for in-demand roles such as cybersecurity technologists and software developers By Michael Hill Sep 29, 2023 4 mins Education Industry Education Industry Education Industry news UK data regulator orders end to spreadsheet FOI requests after serious data breaches The Information Commissioner’s Office says alternative approaches should be used to publish freedom of information data to mitigate risks to personal information By Michael Hill Sep 29, 2023 3 mins Government Cybercrime Data and Information Security feature Cybersecurity startups to watch for in 2023 These startups are jumping in where most established security vendors have yet to go. By CSO Staff Sep 29, 2023 19 mins CSO and CISO Security news analysis Companies are already feeling the pressure from upcoming US SEC cyber rules New Securities and Exchange Commission cyber incident reporting rules don't kick in until December, but experts say they highlight the need for greater collaboration between CISOs and the C-suite By Cynthia Brumfield Sep 28, 2023 6 mins Regulation Data Breach Financial Services Industry Podcasts Videos Resources Events SUBSCRIBE TO OUR NEWSLETTER From our editors straight to your inbox Get started by entering your email address below. Please enter a valid email address Subscribe