{"cve":"CVE-2026-59921","nvd":{"published":"2026-07-28T23:17:09.923","modified":"2026-08-07T15:05:47.990","status":"Analyzed","description":"Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without validating or sanitizing CRLF characters (\\r\\n). Since MIME headers are delimited by CRLF, an attacker who controls the filename can inject arbitrary MIME headers into the multipart body part. The root cause is that neither the encoder nor the FileUpload implementations' setFilename() methods, which only check for null, neutralize CRLF characters before the filename is embedded into the header. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","score":6.5},"cwes":["CWE-93"],"references":["https://github.com/netty/netty/security/advisories/GHSA-gcjf-9mgh-3p7g","https://github.com/netty/netty/security/advisories/GHSA-gcjf-9mgh-3p7g"],"products":["netty:netty"],"source":"nvd","synced_at":"2026-10-19T22:46:40.600842820+00:00"},"epss":{"cve":"CVE-2026-59921","score":0.00465,"percentile":0.40307,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-gcjf-9mgh-3p7g","url":"https://osv.dev/vulnerability/GHSA-gcjf-9mgh-3p7g","summary":"Netty: CRLF Injection via Multipart Filename in Netty HttpPostRequestEncoder","modified":"2026-09-10T03:50:52.172506654Z","packages":[{"ecosystem":"Maven","name":"io.netty:netty-codec-http","purl":"pkg:maven/io.netty/netty-codec-http","ranges":[">=4.2.0.Final <4.2.16.Final"],"fixed":["4.2.16.Final"]},{"ecosystem":"Maven","name":"io.netty:netty-codec-http","purl":"pkg:maven/io.netty/netty-codec-http","ranges":["<4.1.136.Final"],"fixed":["4.1.136.Final"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}