CVE-2025-67735 — netty-codec-http
MEDIUMCVE-2025-67735 is a medium-severity (CVSS 6.5) CWE-93 vulnerability in io.netty:netty-codec-http. A fix is available for io.netty:netty-codec-http — see the affected versions and patch details below.
Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-67735.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-67735 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.netty:netty-codec-http☕io.netty:netty-codec-httpReal-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
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.129.Final and 4.2.8.Final, the io.netty.handler.codec.http.HttpRequestEncoder has a CRLF injection with the request URI when constructing a request. This leads to request smuggling when HttpRequestEncoder is used without proper sanitization of the URI. Any application / framework using HttpRequestEncoder can be subject to be abused to perform request smuggling using CRLF injection. Versions 4.1.129.Final and 4.2.8.Final fix the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-http | ≥ 4.2.0.Alpha1&&< 4.2.8.Final | 4.2.8.Finalio.netty:netty-codec-http:4.2.8.Final |
| ☕Maven | io.netty:netty-codec-http | all versions | 4.1.129.Finalio.netty:netty-codec-http:4.1.129.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-http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-http to 4.2.8.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-67735 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-67735 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-67735. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated Moderate for Red Hat products. A CRLF injection flaw exists in the `io.netty.handler.codec.http.HttpRequestEncoder` component of Netty. This can lead to request smuggling if applications using `HttpRequestEncoder` do not properly sanitize the request URI, allowing an attacker to inject…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat build of Quarkus 3.20.5 | netty-codec-http | RHSA-2026:1899 |
| Red Hat build of Quarkus 3.27.2 | netty-codec-http | RHSA-2026:1965 |
Frequently Asked Questions
Is CVE-2025-67735 in your dependencies?
O3 Security finds CVE-2025-67735 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.