CVE-2026-59920
MEDIUMDescription
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.136.Final and 4.2.16.Final, Netty's STOMP encoder ( StompSubframeEncoder ) does not escape or validate header values in CONNECT and CONNECTED frames, so raw newline ( \n ) characters in a header value are written directly to the wire, allowing an attacker who controls a header value to inject additional STOMP headers. This happens because the encoder intentionally skips escaping for CONNECT/CONNECTED frames per the STOMP 1.2 specification but never rejects the raw newlines, and since a broker parses each line as a separate header, an attacker controlling a value such as a user-supplied login or passcode can overwrite connection parameters or add authentication/role headers to bypass authentication or escalate privileges (the actual impact is broker-dependent). The issue is fixed in versions 4.1.136.Final and 4.2.16.Final.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 15% of all known CVEs.
References
Related Vulnerabilities
Other CWE-93 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-61884 | High | 7.5 | 98% | KEV + Ransom | - |
| CVE-2022-0666 | High | 7.5 | 44% | - | Fix |
| CVE-2016-3115 | Medium | 6.4 | 37% | - | Fix |
| CVE-2024-20337 | High | 8.2 | 30% | - | Fix |
| CVE-2021-39172 | High | 8.8 | 29% | - | Fix |
| CVE-2016-4975 | Medium | 6.1 | 20% | - | Fix |
Common questions
How do I fix CVE-2026-59920?
Upgrade netty to 4.1.136 or later.
Is CVE-2026-59920 being actively exploited?
Not that we know of. CVE-2026-59920 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.
How severe is CVE-2026-59920?
CVE-2026-59920 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-59920 affect?
Published advisories record a fix for netty (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-06.