CVE-2026-34480

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 89% of all CVEs by exploit prediction. 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
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters.

The impact depends on the StAX implementation in use:

* JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records. * Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger.

Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output.

CVSS v3
7.5
EG Score
7.5(medium)
EPSS
54.4%
KEV
Not listed

Published

April 10, 2026

Last Modified

April 24, 2026

Advisory Details (6)

Auto-updated Jun 15, 2026
Patch available. Sources: github_pr.
generic

oss-security - CVE-2026-34480: Apache Log4j Core: Silent log event loss in XmlLayout due to unescaped XML 1.0 forbidden characters

http://www.openwall.com/lists/oss-security/2026/04/10/9
generic

Security :: Apache Logging Services

https://logging.apache.org/security.html#CVE-2026-34480
generic

Layouts :: Apache Log4j

https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout
generic
https://logging.apache.org/cyclonedx/vdr.xml
generic
https://lists.apache.org/thread/5x0hcnng0chhghp6jgjdp3qmbbhfjzhb
github_pr Patch Available

XmlLayout: replace invalid XML characters with U+FFFD

Patch available: apache/logging-log4j2 rel/2.25.4 (PR #4077 merged 2026-03-24)

https://github.com/apache/logging-log4j2/pull/4077

Vendor Advisories for CVE-2026-34480(6)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatlog4j-core-test2026-06-02redhat
redhatoffline-knowledge-portal/rhokp-rhel9:17799969992026-05-28redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.apache.logging.log4j:log4j-core3.0.0-alpha1, 3.0.0-beta1, 3.0.0-beta2, 3.0.0-beta3——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 41× 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 106 total refreshes for this CVE.

  1. 2026-07-15 16:57 UTCEPSS rescore
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  19. 2026-06-15 04:23 UTCVendor advisory
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  25. 2026-06-11 20:07 UTCVendor advisory
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  29. 2026-06-10 13:02 UTCEG score recompute
  30. 2026-06-10 13:02 UTCVendor advisory
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  38. 2026-06-08 08:16 UTCVendor advisory
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  40. 2026-06-07 20:09 UTCVendor advisory
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  44. 2026-06-07 08:02 UTCEG score recompute
  45. 2026-06-07 08:02 UTCVendor advisory
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Frequently asked(5)

What is CVE-2026-34480?
CVE-2026-34480 is a high vulnerability published on April 10, 2026. Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or…
When was CVE-2026-34480 disclosed?
CVE-2026-34480 was first published in the National Vulnerability Database on April 10, 2026, with the most recent update on April 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34480 actively exploited?
CVE-2026-34480 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 54.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-34480?
CVE-2026-34480 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-34480?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34480, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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