Apache Log4j Core XmlLayout XML character sanitization flaw
Apache Log4j Core XmlLayout, in versions up to and including 2.25.3, does not sanitize characters forbidden by the XML 1.0 specification before emitting XML log output. When a log message or MDC value contains such forbidden characters, XmlLayout can generate invalid XML. The observed behavior depends on the StAX implementation in use: with the JRE built-in StAX implementation, forbidden characters are written into the output, producing malformed XML documents; with alternative StAX implementations such as Woodstox, the logging call can throw an exception and the log event is not delivered to the intended appender, instead only appearing in Log4j's internal status logger.
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Impact, mitigation & remediation
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Impact
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Mitigation
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Remediation
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Exploits
No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.
All candidate exploits were filtered out by Mallory's validation.
Affected products & vendors
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
10 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability in Oracle Communications addressed as part of a consolidated fix bundled with CVE-2026-34481.
A high-severity vulnerability affecting HPE Telco Universal SLA Management 4.6 and earlier, associated with potential denial of service and/or CRLF injection impact according to the bulletin.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.