Muhstik Botnet Targeting Redis Servers Using Recently Disclosed Vulnerability

Oracle WebLogic Server (CVE-2017-10271) contains a remote code execution flaw in its WLS Security component, where an XMLDecoder deserialization bug allows unauthenticated attackers to execute arbitrary code. The flaw is triggered by sending specially crafted XML requests to exposed WebLogic HTTP endpoints, so any instance whose WebLogic ports are reachable by untrusted users is at risk. Successful exploitation yields arbitrary code execution on the application server host, and the bug has been widely leveraged to install cryptominers and ransomware payloads. Organizations running Oracle WebLogic Server — particularly instances directly exposed to the internet — are affected, and the flaw has been on CISA's Known Exploited Vulnerabilities catalog since 2022-02-10 with confirmed ransomware use. Exploitation is assessed as essentially certain in the near term (EPSS 100.0%, 100th percentile), and defenders should treat it as an actively exploited, high-priority issue.

Do: Apply Oracle's updates for CVE-2017-10271 per Oracle's instructions (the vendor's required action for this KEV entry). Until patched, restrict network access to WebLogic HTTP/admin ports from untrusted networks and limit or remove access to the XML/WSAT endpoints used for exploitation. Because ransomware operators are known to exploit this flaw, review internet-exposed WebLogic instances for signs of compromise, such as unexpected processes, new scheduled tasks, webshells, or ransomware artifacts.

CVE-2018-7600, widely known as 'Drupalgeddon 2', is an unauthenticated remote code execution flaw in Drupal Core caused by insufficient input validation (CWE-20) in how the CMS processes certain structured request data. It can be triggered through multiple attack vectors, such as crafted parameters submitted to commonly used form and rendering features that are reachable by anonymous users with a single HTTP request. Successful exploitation lets an attacker run arbitrary code under the web application, typically resulting in complete site compromise, and CISA notes the flaw has been used in ransomware operations. Any site running unpatched Drupal 7.x or 8.x core is affected; Drupal's installed base at the time of disclosure was on the order of one million sites. Exploitation is confirmed in the wild (CISA KEV, added 2021-11-03), EPSS assigns a 100% probability of exploitation within 30 days, and no public PoC is recorded in the supplied data.

Do: Upgrade immediately per vendor instructions: Drupal 7.58, 8.5.1, or the corresponding 8.4.6/8.3.9 updates if you remain on older 8.x branches, prioritizing internet-facing sites. Because this flaw has been exploited in the wild and used in ransomware operations, also check patched sites for backdoors, unexpected administrator accounts, modified core files, and rotate credentials.

CVE-2019-2725 is an easily exploitable injection flaw (CWE-74) in the Web Services subcomponent of Oracle WebLogic Server within Oracle Fusion Middleware, publicly documented as affecting WebLogic 10.3.6.0, 12.1.3.0, 12.2.1.1 and 12.2.1.3. It is triggered when an unauthenticated remote attacker sends attacker-controlled XML over HTTP to the WebLogic Web Services async response endpoint (the /_async/AsyncResponseService servlet), which processes the input unsafely. Successful attacks give the attacker takeover of the affected WebLogic server (remote code execution); in the 2019 exploitation wave this was used to install cryptocurrency miners and deploy ransomware. Any organization running affected Oracle WebLogic Server versions is exposed, with the greatest risk where the async/Web Services endpoints are reachable, especially on internet-facing servers. Exploitation is confirmed in the wild: CISA added the CVE to its KEV catalog on 2022-01-10 with ransomware use known and requires applying vendor updates, the EPSS probability of exploitation is 100% (100th percentile), and no public PoC is catalogued.

Do: Apply Oracle's updates per vendor instructions: this CVE was fixed by Oracle's April 2019 out-of-band WebLogic patch and is covered by subsequent Critical Patch Updates, so bring affected WebLogic 10.3.6.0/12.1.3.0/12.2.1.x servers to a patched level (CISA KEV requires this action). Until patched, restrict or remove the async response service deployments (wls9_async_response.war / wls_wsee_async_response.war, exposing the /_async/AsyncResponseService endpoint) and keep WebLogic ports off the internet. Also review logs for unsolicited POSTs to /_async/AsyncResponseService and for signs of dropped miners or ransomware payloads.

CVE-2021-26084 is an OGNL injection vulnerability (CWE-917) in Atlassian Confluence Server and Data Center that may allow an unauthenticated attacker to execute arbitrary code. Any organization running Confluence Server or Data Center is potentially affected. It is significant because it is listed in CISA's Known Exploited Vulnerabilities catalog with known ransomware use, and EPSS assigns a 100.0% probability of exploitation within 30 days (100th percentile).

Do: Apply updates to Confluence Server and Data Center per Atlassian's instructions, which is the required action in the CISA KEV listing. Prioritize remediation given confirmed in-the-wild exploitation and known ransomware use.

Apache Log4j2, an extremely widely used Java logging library, fails to protect its JNDI lookup feature against attacker-controlled JNDI-related endpoints (CWE-20, CWE-502), so crafted text processed by the logger causes the Java runtime to fetch and load attacker-supplied objects, leading to remote code execution. The flaw is triggered whenever attacker-controlled input reaches the logging API and is parsed for JNDI lookups, a pattern common in web servers and enterprise Java applications that log user-supplied fields such as headers or form values. Successful exploitation yields arbitrary code execution under the privileges of the affected application, giving attackers a foothold for lateral movement, data theft, and ransomware deployment. Any Java application or product that ships or bundles an affected Apache Log4j2 release is exposed, making this one of the most broadly deployed vulnerabilities ever disclosed. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-10 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days.

Do: Inventory all Java applications and dependencies for Apache Log4j2 and apply the vendor's patched updates, or remove affected assets from the network, as required by CISA's KEV catalog. Where updates are not yet available, use the temporary mitigations in CISA's ED-22-02 recommended-mitigation guidance, such as disabling message lookups, only until patches are applied. Prioritize internet-facing and business-critical systems and hunt for exploitation activity given known ransomware use.

CVE-2022-0543 is a Debian-specific Lua sandbox escape in the Redis key-value database, caused by a packaging issue in how the Debian-distributed redis-server build ships its embedded Lua interpreter (tracked as CWE-862). A remote, unauthenticated attacker can send a crafted Lua script through Redis' scripting interface (EVAL) to escape the Lua sandbox that normally limits scripts to safe operations. Successful exploitation yields remote code execution on the server in the context of the Redis process, giving the attacker control over stored data and the ability to run arbitrary system commands. Only Redis servers installed from Debian's (and derivative distributions') packages are affected; upstream Redis builds are not impacted. The flaw is actively exploited: CISA added it to the Known Exploited Vulnerabilities catalog on 2022-03-28, EPSS puts the 30-day exploitation probability at 99.4% (100th percentile), and botnet/worm activity against exposed Redis servers has been widely reported.

Do: Apply the updated redis-server packages published through Debian security updates (and equivalent updates in derivative distributions) per vendor instructions, restarting the Redis service after patching. As interim mitigation, restrict Redis exposure by binding to trusted interfaces only, enabling authentication, and firewalling port 6379 from untrusted networks. Check affected hosts for signs of compromise, such as unexpected Lua EVAL activity, unfamiliar child processes, or connections consistent with botnet/worm traffic.