CVE-2026-49844Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson()
- 6.3MediumCVSS base score
- 0.60%Exploitation in 30 daysEPSS · top 51% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not permit these tokens, so a conformant parser rejects the resulting document. The defect is reachable only when both of the following conditions hold: * The application uses the message resolver https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message of JsonTemplateLayout or any other layout that relies on MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{"JSON"}). * The application logs a MapMessage that contains an attacker-controlled floating-point value. An attacker who can supply a non-finite value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log record or disrupt downstream log ingestion and parsing. Users are advised to upgrade to Apache Log4j API 2.25.5 or 2.26.1, both of which emit RFC 8259-compliant JSON for non-finite values.
Timeline
ID reserved
By apache
- 39 days later
· 39 days later
Published
- 2 months later
· 2 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| apacheCNA (assigner) | 4.0 | Medium6.3 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N |
| NVDNVD · Analyzed | 4.0 | Medium6.3 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.60% · top 51% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.
Affected products
Apache Software Foundation · Apache Log4j API
- affected 2.13.1 – < 2.25.5
- affected 2.26.0 – < 2.26.1
- affected 3.0.0-alpha1 – ≤ 3.0.0-beta2
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Mavenorg.apache.logging.log4j:log4j-apiGHSA-qv9r-c865-cp47 (opens in a new tab)
References
References4
- https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message (opens in a new tab)related
- https://github.com/apache/logging-log4j2/pull/4163 (opens in a new tab)patch
- https://logging.apache.org/cyclonedx/vdr.xml (opens in a new tab)vendor-advisory
- https://logging.apache.org/security.html#CVE-2026-49844 (opens in a new tab)vendor-advisory
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-43102 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-qv9r-c865-cp47 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-49844)Record last updated .