Vulnerability in Netty
CVE-2026-33870
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.132.Final and 4.2.10.Final, Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks. Versions 4.1.132.Final and 4.2.10.Final fix the issue.
Vulnerability class: HTTP Request Smuggling
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.007 (51.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.007 · change: +0.001
Affected products
- Netty — versions < 4.1.132.Final, >= 4.2.0.Alpha1, < 4.2.10.Final
Weakness classification (CWE)
References
- github.com/netty/netty/security/advisories/GHSA-pwqr-wmgm-9rr8 (Exploit, Mitigation, Vendor Advisory)
- w4ke.info/2025/06/18/funky-chunks.html (Technical Description)
- w4ke.info/2025/10/29/funky-chunks-2.html (Technical Description)
- www.rfc-editor.org/rfc/rfc9110 (Technical Description)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-33870?
- CVE-2026-33870 is a high-severity vulnerability in Netty, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 7.5/10. Published 2026-03-27.
- How severe is CVE-2026-33870?
- High severity. CVSS v3 base score is 7.5 out of 10.