# Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout

Advisory record · `GHSA-w35j-pv5h-q9q9`

- **Identifiers:** `GHSA-w35j-pv5h-q9q9` · `CVE-2026-34481`
- **State:** Confirmed
- **Severity:** CVSS 6.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-116](https://cwe.mitre.org/data/definitions/116.html)
- **Tags:** [CWE-116](https://agentprime.io/advisories/tag/cwe-116.md)
- **Published:** 10 Apr 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 10 Apr 2026, 18:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `org.apache.logging.log4j:log4j-layout-template-json` (Maven): affected `>=2.14.0, <2.25.4 || >=3.0.0-alpha1, <=3.0.0-beta3`; fixed in `2.25.4`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Apache Log4j's log4j-layout-template-json, versions 2.14.0 up to 2.25.4 (excluding 2.25.4) and 3.0.0-alpha1 through 3.0.0-beta3, produces invalid JSON when log events contain NaN, Infinity, or -Infinity values. An attacker who can supply a floating-point value that the application logs through a MapMessage, in an application using JsonTemplateLayout, can cause downstream log processors to reject or fail to index those records. Upgrade to log4j-layout-template-json 2.25.4.

Written 2 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N`, from CNA (apache)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0072, the 54th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:16 UTC: First seen by agentprime
- 31 Oct 2026, 14:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-w35j-pv5h-q9q9)

## Sources

- [GitHub Advisory Database: GHSA-w35j-pv5h-q9q9](https://github.com/advisories/GHSA-w35j-pv5h-q9q9)
- [OSV: GHSA-w35j-pv5h-q9q9](https://osv.dev/vulnerability/GHSA-w35j-pv5h-q9q9)
- <https://nvd.nist.gov/vuln/detail/CVE-2026-34481>
- <https://github.com/apache/logging-log4j2/pull/4080>
- <https://github.com/apache/logging-log4j2>
- <https://lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcv>
- <https://logging.apache.org/cyclonedx/vdr.xml>
- <https://logging.apache.org/log4j/2.x/manual/json-template-layout.html>
- <https://logging.apache.org/security.html#CVE-2026-34481>
- <http://www.openwall.com/lists/oss-security/2026/04/10/10>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-w35j-pv5h-q9q9>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-w35j-pv5h-q9q9/>. Everything for agents: <https://agentprime.io/llms.txt>.