CVE-2026-19203
CVE-2026-19203 is a CWE-444 vulnerability. O3 Security confirms whether CVE-2026-19203 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
A client may issue specially crafted HTTP/1.1 chunked requests to a Jetty server that cause Jetty and an intermediary proxy to interpret different request boundaries, potentially resulting…
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-19203.
Description
A client may issue specially crafted HTTP/1.1 chunked requests to a Jetty server that cause Jetty and an intermediary proxy to interpret different request boundaries, potentially resulting in HTTP request smuggling.
This is caused by Jetty accepting a lone LF character as a terminator in parts of chunked request parsing. Depending on the Jetty version and configured HTTP compliance mode, this may occur in chunk extensions, chunk data termination, or trailer termination.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. 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.
Remediation status
No patched version of the affected component has shipped for CVE-2026-19203 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2026-19203 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-2026-19203. 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-2026-19203 in your dependencies?
O3 detects CVE-2026-19203 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.