PT-2026-31943 · Apache · Apache Log4J+1

Ap4Sh · CVE-2026-34481 · Published 2026-04-10 · Updated 2026-07-24

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Name of the Vulnerable Software and Affected Versions Apache Log4j versions up to and including 2.25.3

Description Apache Log4j's JsonTemplateLayout generates invalid JSON output when processing log events that include non-finite floating-point values (NaN, Infinity, or -Infinity), violating RFC 8259 standards. This can lead to downstream log processing systems rejecting or failing to index affected records. Exploitation requires the application to use JsonTemplateLayout and log a MapMessage containing a floating-point value controlled by an attacker.

Recommendations Upgrade to Apache Log4j JSON Template Layout 2.25.4.

Exploit

Fix

Improper Encoding or Escaping of Output

Weakness Enumeration

CWE-116

Related Identifiers

CLEANSTART-2026-CG99434

CVE-2026-34481

GHSA-W35J-PV5H-Q9Q9

OESA-2026-3153

OPENSUSE-SU-2026:10544-1

SUSE-SU-2026:1843-1

Affected Products

Apache Log4J

Jsontemplatelayout

References · 63

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34481.json · Exploit
• https://github.com/apache/logging-log4j2/pull/4080 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-49844 · Security Note
• https://security-tracker.debian.org/tracker/CVE-2026-34481 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2026-34481 · Vendor Advisory
• https://logging.apache.org/security.html#CVE-2026-34481 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-34479 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-22444 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-34481 · Security Note
• https://logging.apache.org/cyclonedx/vdr.xml · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-34480 · Security Note
• https://osv.dev/vulnerability/CLEANSTART-2026-CG99434 · Vendor Advisory
• https://osv.dev/vulnerability/OESA-2026-3153 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2026:10544-1 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-24281 · Security Note