No exploitation reportedFix available

CVE-2026-33557

Q: Is CVE-2026-33557 actively exploited?

Active exploitation of CVE-2026-33557 has not been confirmed. Its EPSS score was 0.9% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-33557?

CVE-2026-33557 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L.

No exploitation reported by the sources we read.

Published2026-04-20
Fixed in4.1.2
WeaknessCWE-1285 · CWE-303

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A possible security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbearer.jwt.validator.class` is set to `org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator`. It accepts any JWT token without validating its signature, issuer, or audience. An attacker can generate a JWT token from any issuer with the `preferred_username` set to any user, and the broker will accept it. We advise the Kafka users using kafka v4.1.0 or v4.1.1 to set the config `sasl.oauthbearer.jwt.validator.class` to `org.apache.kafka.common.security.oauthbearer.BrokerJwtValidator` explicitly to avoid this vulnerability. Since Kafka v4.1.2 and v4.2.0 and later, the issue is fixed and will correctly validate the JWT token.

Timeline

dates in UTC

2026-04-2014:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33557?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33557?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Apache kafka

Branch	Affected	Fixed in	Source
4.1	≥ 4.1.0, < 4.1.2	4.1.2	NVD · OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Apache kafka to 4.1.2

Advisories and patches

kafka.apache.orgVendor Advisory
lists.apache.orgMitigation · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-04-20
OpenCVESSVC decisionnone—
CISA-ADPCVSS 3.19.12026-04-20
CNACVSS 3.18.6read 2026-10-23
CNAweakness (CWE)CWE-1285, CWE-303read 2026-10-23
FIRST EPSSEPSS score0.9 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
Published: 2026-04-20
Last Modified: 2026-07-15
NVD status: Modified

Frequently asked questions

What is CVE-2026-33557?

Is CVE-2026-33557 actively exploited?

Active exploitation of CVE-2026-33557 has not been confirmed. Its EPSS score was 0.9% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-33557?

CVE-2026-33557 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L.

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