What is CVE-2020-2883?
CVE-2020-2883 is a critical deserialization vulnerability affecting Oracle WebLogic Server, a widely used Java EE application server. The flaw resides within the com.tangosol.coherence.mvel2.sh.ShellSession class, which improperly handles deserialized user input, leading to arbitrary remote code execution (RCE). Attackers can exploit this vulnerability to execute malicious commands on the underlying system without authentication, making it a high-severity security threat. The vulnerability received a CVSS score of 9.8, indicating its critical nature and ease of exploitation. Oracle WebLogic Server versions 10.3.6.0.0, 12.1.3.0.0, and 12.2.1.4.0 were found to be vulnerable, but Oracle released a security update for such vulnerable versions on the day CVE-2020-2883 was published.
When Was the Vulnerability Discovered?
CVE-2020-2883 was publicly disclosed in Oracle’s April 2020 Critical Patch Update (CPU), released on April 14, 2020, but the fact that CISA added it to their Known Exploited Vulnerabilities (KEV) Catalog this past January 2025, brings it back into the spotlight, highlighting how there may be a significant amount of vulnerable infrastructure still up for grabs by threat actors. The vulnerability was discovered by security researchers who identified a flaw in the way WebLogic Server processes serialized data. Researchers from KnownSec 404 Team and others contributed to the initial identification and proof-of-concept (PoC) exploits that demonstrated the severity of the issue. Armis Centrix™ for Early Warning, added CVE-2020-2883 to the list of known vulnerabilities being exploited in the wild on April 14, 2020 (the same day of the public disclosure), while CISA added CVE-2020-2883 to their KEV catalog on January 7, 2025, making Armis Centrix™ for Early Warning early by a staggering 1729 days.
Significance CVE-2020-2883:
Vulnerable component: the vulnerability primarily affects the Coherence library in WebLogic Server, which is responsible for handling distributed caching and data grid computations. The flaw stems from the server’s failure to properly validate user-supplied serialized input, enabling attackers to craft a malicious payload that leads to remote code execution. Because WebLogic often runs with high privileges in enterprise environments, successful exploitation could allow full control over the affected system, leading to data theft, system compromise, and lateral movement within the network.
Exploitation scenario: an attacker could send a specially crafted HTTP request containing a maliciously serialized object to the vulnerable WebLogic instance. Once deserialized, the object triggers the execution of arbitrary code on the server, allowing the attacker to install backdoors, exfiltrate sensitive data, or use the compromised system as a foothold for further attacks. The exploit does not require authentication, making it highly attractive for adversaries scanning the internet for unpatched WebLogic servers.
Impact and blast radius: there is no way around it, the potential blast radius of this vulnerability was (and still is) significant. WebLogic is commonly used in enterprises, including financial institutions, government agencies, and cloud-hosted environments. A successful exploit could result in large-scale data breaches, operational disruptions, and compliance violations. Additionally, WebLogic has historically been a frequent target of ransomware groups and botnets, such as the DarkIRC botnet, which weaponizes WebLogic vulnerabilities for mass exploitation given its market penetration.
Value of Timely Awareness: timely awareness of CVE-2020-2883 is crucial due to the history of WebLogic vulnerabilities being rapidly weaponized by attackers. Within days of the public disclosure, proof-of-concept (PoC) exploits were circulating in underground forums, leading to widespread scanning and exploitation attempts. No matter whether reacting to the initial disclosure by Oracle, Armis Centrix™ for Early Warning’s bulletin or CISA KEV’s more recent release, organizations relying on WebLogic Server needed and still need to act swiftly to assess their exposure, apply patches, and implement additional security measures to mitigate the risk of compromise.
Mitigation and Protection:
Proactive defense and workarounds: to protect against CVE-2020-2883, organizations should immediately apply Oracle’s security patches released in the April 2020 Critical Patch Update. If patching is not feasible, implementing workarounds such as disabling T3/IIOP protocol or restricting network access to WebLogic services can reduce exposure to remote attacks. Additionally, deploying Web Application Firewalls (WAFs) with rules designed to detect and block malicious serialized objects can provide an added layer of defense. Security teams should also monitor WebLogic logs for unusual activity, such as unauthorized access attempts or execution of unexpected commands, which could indicate an exploitation attempt.
Continuous monitoring and updates: on top of continuous monitoring and timely application of updates, security teams should leverage Intrusion Detection Systems (IDS) and Endpoint Detection and Response (EDR) solutions to detect potential exploitation attempts. Regular vulnerability assessments and penetration testing can help identify exposed systems before attackers do. Given WebLogic’s frequent history of critical vulnerabilities, adopting a proactive security strategy, such as isolating WebLogic deployments in hardened environments and enforcing least privilege principles, can minimize the risk of future attacks. By implementing strong security practices, organizations can effectively mitigate the risks posed by CVE-2020-2883 and safeguard their WebLogic deployments from exploitation.
Stay vigilant and ensure your systems are up-to-date to defend against evolving cybersecurity threats.
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