VulnerabilityPublished 26 Oct 2026

CVE-2026-116542: netty-tcnative · Improper Handling of Unicode Encoding

Affects netty-tcnativeSource CVE Database V5

Not known to be exploited · CVSS 6.9 Medium : upgrade to 2.0.84.Final when convenient.

Data as of 26 Oct 2026, 16:53 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 2.0.84.Final

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade netty-tcnative and netty-tcnative-boringssl-static and netty/io.netty:netty-tcnative and netty/io.netty:netty-tcnative-boringssl-static to 2.0.84.Final.

Affected software

Product	Affected	Fixed in
netty-tcnativeio.netty:netty-tcnative	Affected <2.0.84.Final	Fixed in 2.0.84.Final
netty-tcnative-boringssl-staticio.netty:netty-tcnative-boringssl-static	Affected <2.0.84.Final	Fixed in 2.0.84.Final
Mavennetty/io.netty:netty-tcnative`pkg:maven/netty/io.netty:netty-tcnative`Other threats	Affected <2.0.84.Final	Fixed in 2.0.84.Final
Mavennetty/io.netty:netty-tcnative-boringssl-static`pkg:maven/netty/io.netty:netty-tcnative-boringssl-static`Other threats	Affected <2.0.84.Final	Fixed in 2.0.84.Final

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade netty-tcnative to version 2.0.84.Final or later, where this vulnerability is fixed. No other mitigation or temporary workaround is indicated by the vendor advisory.

Description

CVE-2026-116542 is a vulnerability in netty-tcnative versions before 2.0.84.Final that allows remote unauthenticated clients to spoof SNI hostnames by exploiting improper handling of Unicode encoding in JNI NewStringUTF decoding. Attackers can use overlong encodings in the ClientHello server_name field to manipulate SNI-based certificate selection, access control decisions, and logging.

Impact

This vulnerability allows remote unauthenticated attackers to spoof SNI hostnames, potentially bypassing hostname-based certificate validation and access controls. It may also cause inaccurate logging of hostnames, which can hinder incident response and auditing. The CVSS 4.0 base score is 6.9 (medium severity), reflecting network attack vector, no privileges required, no user interaction, and low impact on integrity.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 15:33 UTC

Technical details

References

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