Log4j FilteredObjectInputStream Bypass: Pre-auth RCE via MarshalledObject
github.com | vulnerability | Critical | #rce | #public-poc | #java | #deserialization | #pre-auth | #authentication | #vulnerability | #log4j | #apache | #commons-collections | #serialization | #poc | #filteredobjectinputstream | #marshalledobject
Summary
Pre-auth RCE on Java services deserializing LogEvent: Log4j's FOIS allowlist falls to LogEventProxy's MarshalledObject, whose .get() opens an unfiltered stream, executing hidden CC6 gadget chains.
Why it matters
This PoC demonstrates an unexpected filter-bypass gadget in Log4j 2, emphasizing the danger of unauthenticated serialized object ingestion.
- Vendor
- Apache
- Product
- Log4j 2
- Affected versions
- log4j-api 2.11.0–2.24.3, log4j-core 2.8.0–2.24.3
- CVSS
- 9.8
- Published
- Collected
--- id: 6756 title: "Log4j FilteredObjectInputStream Bypass: Pre-auth RCE via MarshalledObject" cvss: 9.8 severity: critical vendor: "Apache" product: "Log4j 2" affected_versions: "log4j-api 2.11.0–2.24.3, log4j-core 2.8.0–2.24.3" source_domain: github.com source_url: "https://github.com/hypnguyen1209/log4j2-rce" published_at: "2026-08-26T15:44:51Z" tags: ["rce", "public-poc", "java", "deserialization", "pre-auth", "authentication", "vulnerability", "log4j", "apache", "commons-collections", "serialization", "poc", "filteredobjectinputstream", "marshalledobject"] phying_url: "https://phying.com/item/6756" lang: en --- # Log4j FilteredObjectInputStream Bypass: Pre-auth RCE via MarshalledObject ## Summary Pre-auth RCE on Java services deserializing LogEvent: Log4j's FOIS allowlist falls to LogEventProxy's MarshalledObject, whose .get() opens an unfiltered stream, executing hidden CC6 gadget chains. ## Why it matters This PoC demonstrates an unexpected filter-bypass gadget in Log4j 2, emphasizing the danger of unauthenticated serialized object ingestion. ## Intelligence Metadata - **Sources:** github.com - **CVSS:** 9.8 - **Vendor:** Apache - **Product:** Log4j 2 - **Affected versions:** log4j-api 2.11.0–2.24.3, log4j-core 2.8.0–2.24.3 - **Published:** 2026-08-26T15:44:51Z - **Original:** https://github.com/hypnguyen1209/log4j2-rce - **Phying News:** https://phying.com/item/6756