CVE-2026-42585: netty Request Smuggling

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.02%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-444 CWE-444

Affected Products

Vendor	Product	Versions
netty	netty	< 4.1.133
netty	netty	4.2.0 — 4.2.13

References

Advisories & Patches

https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv

Exploits

https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv

Frequently Asked Questions

What is CVE-2026-42585? +

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-42585? +

CVE-2026-42585 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42585? +

CVE-2026-42585 affects products from netty, specifically: netty. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42585? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-42585