CVE-2026-93566VulnerabilityPublished 18 Sep 2026Updated 6 Nov 2026

Summary Netty skips strict chunk size line validation when the line has no chunk extension (;), so a chunk size line

Source GCVE Database

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Authoritative record:CVE-2026-93566· Medium 6.5

Not known to be exploited · CVSS 6.5 Medium : update Red Hat build of Keycloak 26.4 when convenient.

Data as of 6 Nov 2026, 14:05 UTC

CVSS 3.1 base score

6.5Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (redhat)	CVSS 3.1	6.5

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
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 on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

ghsa-9mrj-55p4-qwf4

What to do

Patches and advisories

Affected software

Product	Affected	Fixed in
Red Hat Build of Debezium 3.6netty-codec-http	Affected–	Fixed in–
Red Hat build of Keycloak 26.4keycloak-rhel9-container	Affected–	Fixed in–
Red Hat build of Keycloak 26.4keycloak-rhel9-operator-bundle-container	Affected–	Fixed in–
Red Hat build of Keycloak 26.4keycloak-rhel9-operator-container	Affected–	Fixed in–
Red Hat build of Keycloak 26.6.8netty-codec-http	Affected–	Fixed in–
Red Hat build of Quarkus 3.27.5.SP2netty-codec-http	Affected–	Fixed in–

AI-suggested

A security update addressing this vulnerability is available. Users should apply the official patch provided by the vendor. The Red Hat advisory references an update in Red Hat build of Quarkus 3.33.3.SP2 that includes security fixes. No indication of 'no action required' or 'already mitigated' is present, so applying the vendor's update is recommended.

Description

Netty's HTTP decoder skips strict validation of chunk size lines when no chunk extension is present, allowing malformed chunk size lines containing embedded bare carriage return characters to be accepted. This behavior violates RFC 9112's chunk-size syntax and enables HTTP request smuggling attacks.

Impact

An attacker can exploit this vulnerability to perform HTTP request smuggling attacks, potentially allowing them to bypass security controls, poison caches, or interfere with request routing. The CVSS score of 6.5 (medium severity) reflects the network attack vector, low attack complexity, no privileges required, no user interaction, and impacts on confidentiality and integrity but not availability.

References

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