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CVE-2026-34479 is a vulnerability in the Apache Log4j 1-to-Log4j 2 bridge, specifically in the Log4j1XmlLayout implementation provided by the org.apache.logging.log4j:log4j-1.2-api component. The layout fails to properly escape characters forbidden by the XML 1.0 specification when rendering log events as XML. As a result, log output can become malformed and non-conforming XML parsers will reject the affected documents with a fatal parsing error. The issue affects deployments that use Log4j1XmlLayout directly in a Log4j Core 2 configuration, as well as deployments using the Log4j 1 compatibility layer with the legacy XMLLayout class mapped through the bridge. Affected versions include 2.x releases from 2.7 before 2.25.4 and 3.x prerelease versions from 3.0.0-alpha1 through 3.0.0-beta2.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
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.