CVE-2026-49844

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under NVD CVSS v3. EPSS exploit probability: 0.8% (55th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.8%CVSS: 5.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
5.9
EG Score
5.9MEDIUMmedium confidence
EG Risk
27
EG Risk 27/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation1% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.8%
EPSS %ILE
55th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 10, 2026

Last Modified

September 17, 2026

Advisory Details (4)

Auto-updated Jul 10, 2026
Patch available. Sources: github_pr.
genericMentions a patch (unverified)

Security :: Apache Logging Services

https://logging.apache.org/security.html#CVE-2026-49844
generic

JSON Template Layout :: Apache Log4j

https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message
genericMentions a patch (unverified)
https://logging.apache.org/cyclonedx/vdr.xml
github_pr

Fix handling of non-finite numbers while encoding `MapMessage` to JSON

Fix merged in apache/logging-log4j2 PR #4163 on 2026-06-29 — awaiting tagged release

https://github.com/apache/logging-log4j2/pull/4163

Vendor Advisories for CVE-2026-49844(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
apache-log4j22.13.3-1 ... 2.19.0-2 (17 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
apache-log4j22.19.0-2
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
apache-log4j22.19.0-2
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
apache-log4j22.19.0-2
  • every version on: no fix on record
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
org.apache.logging.log4j:log4j-api2.26.0
  • 2.13.1 up to 2.25.5: fixed in 2.25.5
  • 2.26.0 up to 2.26.1: fixed in 2.26.1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 28× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 144 total refreshes for this CVE.

  1. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
  4. 2026-10-06 15:18 UTCEPSS rescore
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  9. 2026-10-01 14:56 UTCEG score recompute
  10. 2026-09-30 15:03 UTCEPSS rescore
  11. 2026-09-28 13:51 UTCEPSS rescore
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  13. 2026-09-27 13:48 UTCEPSS rescore
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  16. 2026-09-24 11:08 UTCEG score recompute
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  22. 2026-09-16 14:08 UTCEPSS rescore
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  24. 2026-09-14 08:38 UTCEG score recompute
  25. 2026-09-13 16:47 UTCEPSS rescore
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  1. 2026-09-13 08:10 UTCEG score recompute
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  3. 2026-09-11 14:53 UTCEPSS rescore
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  5. 2026-09-08 22:01 UTCEPSS rescore
  6. 2026-09-08 02:42 UTCEG score recompute
  7. 2026-09-07 16:01 UTCEPSS rescore
  8. 2026-09-06 13:47 UTCEPSS rescore
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  10. 2026-09-04 05:06 UTCEPSS rescore
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  27. 2026-08-21 23:49 UTCEPSS rescore
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  40. 2026-08-15 01:30 UTCEPSS rescore
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  42. 2026-08-13 22:00 UTCEPSS rescore
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  44. 2026-08-12 20:22 UTCGHSA enrichment
  45. 2026-08-12 13:51 UTCEPSS rescore
  46. 2026-08-11 19:52 UTCEG score recompute
  47. 2026-08-11 19:52 UTCGHSA enrichment
  48. 2026-08-11 00:00 UTCEPSS rescore
  49. 2026-08-10 19:24 UTCGHSA enrichment
  50. 2026-08-09 18:55 UTCEG score recompute
  51. 2026-08-09 18:55 UTCGHSA enrichment
  52. 2026-08-09 13:46 UTCEPSS rescore
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  54. 2026-08-08 18:27 UTCGHSA enrichment
  55. 2026-08-08 16:37 UTCEPSS rescore
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  57. 2026-08-07 17:58 UTCGHSA enrichment
  58. 2026-08-06 17:29 UTCEG score recompute
  59. 2026-08-06 17:29 UTCGHSA enrichment
  60. 2026-08-06 13:47 UTCEPSS rescore
  61. 2026-08-05 19:17 UTCEPSS rescore
  62. 2026-08-05 17:01 UTCGHSA enrichment
  63. 2026-08-04 16:32 UTCEG score recompute
  64. 2026-08-04 16:32 UTCGHSA enrichment
  65. 2026-08-04 15:10 UTCEPSS rescore
  66. 2026-08-04 10:39 UTCEPSS rescore
  67. 2026-08-03 16:02 UTCEG score recompute
  68. 2026-08-03 16:02 UTCGHSA enrichment
  69. 2026-08-03 10:36 UTCEPSS rescore
  70. 2026-08-02 15:34 UTCEG score recompute
  71. 2026-08-02 15:34 UTCGHSA enrichment
  72. 2026-08-02 02:27 UTCEPSS rescore
  73. 2026-08-01 15:05 UTCEG score recompute
  74. 2026-08-01 15:05 UTCGHSA enrichment
  75. 2026-08-01 04:16 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-49844?
CVE-2026-49844 is a medium vulnerability published on July 10, 2026. 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…
When was CVE-2026-49844 disclosed?
CVE-2026-49844 was first published on July 10, 2026, with the most recent update on September 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49844 actively exploited?
CVE-2026-49844 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.8% probability of exploitation in the next 30 days (55th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-49844?
CVE-2026-49844 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-49844?
A fix for CVE-2026-49844 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-49844 are linked in the Vendor Advisories panel on this page.

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