# Apache Log4j API: Improper encoding of non-finite floating-point values during MapMessage JSON serialization

Advisory record · `GHSA-qv9r-c865-cp47`

- **Identifiers:** `GHSA-qv9r-c865-cp47` · `CVE-2026-49844`
- **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:** 11 Jul 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 11 Jul 2026, 00:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `org.apache.logging.log4j:log4j-api` (Maven): affected `>=2.13.1, <2.25.5 || >=2.26.0, <2.26.1`; fixed in `2.25.5`, `2.26.1`

## Machine-written summary

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

> Apache Log4j API versions 2.13.1 through 2.25.4 and 2.26.0 can emit invalid JSON when a MapMessage contains a NaN, Infinity, or -Infinity value, because these tokens are not permitted by RFC 8259. An attacker who can supply such a value to an application that logs MapMessage objects through JsonTemplateLayout or another JSON-producing layout can corrupt log records or disrupt downstream log parsing. Upgrade to Apache Log4j API 2.25.5 or 2.26.1.

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:L/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:** 0.0060, the 48th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:17 UTC: First seen by agentprime
- 31 Oct 2026, 14:17 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-qv9r-c865-cp47)

## Sources

- [GitHub Advisory Database: GHSA-qv9r-c865-cp47](https://github.com/advisories/GHSA-qv9r-c865-cp47)
- [OSV: GHSA-qv9r-c865-cp47](https://osv.dev/vulnerability/GHSA-qv9r-c865-cp47)
- <https://nvd.nist.gov/vuln/detail/CVE-2026-49844>
- <https://github.com/apache/logging-log4j2/pull/4163>
- <https://github.com/apache/logging-log4j2/commit/19edb23e162d6c728a8c2221a240037d389ed300>
- <https://github.com/apache/logging-log4j2/commit/feadf8eb0b4acb6ddfa4c0ab2bbc6d88b8e12d82>
- <https://github.com/apache/logging-log4j2>
- <https://github.com/apache/logging-log4j2/releases/tag/rel/2.25.5>
- <https://github.com/apache/logging-log4j2/releases/tag/rel/2.26.1>
- <https://logging.apache.org/cyclonedx/vdr.xml>
- <https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message>
- <https://logging.apache.org/security.html#CVE-2026-49844>

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-qv9r-c865-cp47>, 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-qv9r-c865-cp47/>. Everything for agents: <https://agentprime.io/llms.txt>.