# CVE-2021-44228: Apache Log4j2 Remote Code Execution Vulnerability

- Exploited (CISA KEV): yes, added 2021-12-10, known ransomware use
- Published: 2021-12-10
- CVSS: 10 CRITICAL (v3.1)
- EPSS: 100.0% (100th percentile)
- CWE: CWE-502, CWE-400, CWE-20

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.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Before feed history | — | — |
| AWS | Rule published | 2021-12-10 | 0 |
| Microsoft Azure | Rule published | — | — |
| Google Cloud | Rule published | — | — |
| Fastly | Before feed history | — | — |
| F5 | Before feed history | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

### AWS

- 2021-12-10 · new
  > Known bad inputs Log4JRCE BadAuthToken_COOKIE_AUTHORIZATION: Added the rule Log4JRCE version 1.2 in response to the recently disclosed security issue within Log4j. For information see CVE-2021-44228 . This rule inspects common URI paths, query strings, the first 8KB of the request body, and common headers. The rule uses double URL_DECODE_UNI text transformations. Released version 1.3 of Log4JRCE to tune the matching criteria and to inspect additional headers. Removed the rule BadAuthToken_COOKI…
  Source: https://docs.aws.amazon.com/waf/latest/developerguide/aws-managed-rule-groups-changelog.html

### Microsoft Azure

- undated · listed · rule 944240
  > Rule 944240: Critical - 5 · 2 · Remote Command Execution: Java serialization and Log4j vulnerability (CVE-2021-44228, CVE-2021-45046)
  Source: https://learn.microsoft.com/en-us/azure/web-application-firewall/afds/waf-front-door-drs
- undated · listed · rule 944240
  > Rule 944240: Critical - 5 · 2 · Remote Command Execution: Java serialization and Log4j vulnerability (CVE-2021-44228, CVE-2021-45046)
  Source: https://learn.microsoft.com/en-us/azure/web-application-firewall/ag/application-gateway-crs-rulegroups-rules
- undated · listed · rule 800100
  > Rule 800100: Critical - 5 · PL2 · Rule to help detect and mitigate log4j vulnerability CVE-2021-44228, CVE-2021-45046
  Source: https://learn.microsoft.com/en-us/azure/web-application-firewall/ag/application-gateway-crs-rulegroups-rules

### Google Cloud

- undated · listed · rule owasp-crs-v030001-id044228-cve
  > Signature owasp-crs-v030001-id044228-cve (sensitivity 1): Base rule to help detect exploit attempts of CVE-2021-44228 & CVE-2021-45046
  Source: https://docs.cloud.google.com/armor/docs/waf-rules

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: blocked (2 of 2 requests blocked), template CVE-2021-44228, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: blocked (2 of 2 requests blocked), template CVE-2021-44228, 2026-11-02

## Social

1 posts seen since 2026-11-02.

- x 2026-11-02: Log4Shell (CVE-2021-44228) — 4 years old, still exploited in the wild. CVSS 10.0. One crafted log line → remote code execution via JNDI/LDAP in Log4j2. If you don't know every service that bundles Log4j, you can't call yourself safe. #CVE #InfoSec #ThreatIntel #CyberSecurity (https://x.com/AssurePort/status/2117386833717760173)

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2021-44228 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-44228