CVE-2026-73507 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in io.netty:netty-codec-xml. O3 Security confirms whether CVE-2026-73507 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Netty: Denial of Service in XmlFrameDecoder via CPU Exhaustion
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73507.
Real-World Exposure
io.netty:netty-codec-xml☕io.netty:netty-codec-xmlReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Summary
An attacker can cause Denial of Service by sending a specially crafted malicious XML payload (e.g., repeated </ characters) to a Netty server utilizing XmlFrameDecoder, causing the server's EventLoop thread to exhaust CPU resources and become unresponsive.
Details
io.netty.handler.codec.xml.XmlFrameDecoder suffers from a vulnerability resulting in CPU exhaustion. When < followed by / is encountered, the decoder scans the remaining buffer for a closing >.
Because the parser state is not saved between decode() invocations, an attacker can trickle-feed a payload of </ characters. This forces the decoder to repeatedly rescan the entire accumulated buffer. A 1MB maxFrameLength is enough to completely hang a server's thread while it loops endlessly.
Impact
Denial of Service via CPU Exhaustion. Any application utilizing Netty's XmlFrameDecoder is impacted. An unauthenticated remote attacker can exploit this flaw by sending a modest amount of malformed XML data to an exposed port.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-xml | ≥ 4.2.0.Final&&< 4.2.16.Final | 4.2.16.Final |
| ☕Maven | io.netty:netty-codec-xml | all versions | 4.1.136.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-xml. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update io.netty:netty-codec-xml to 4.2.16.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73507 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-73507 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-73507. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-73507 in your dependencies?
O3 detects CVE-2026-73507 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.