Medium

CVE-2026-33558 — Apache Kafka, Apache Kafka Clients: Information Exposure Through Network Client Log Output

Information exposure vulnerability has been identified in Apache Kafka. The NetworkClient component will output entire requests and responses information in the DEBUG log level in the logs. By default, the log level is set to INFO level. If the DEBUG level is enabled, the sensitive information will be exposed via the requests and responses output log. The entire lists of impacted requests and responses are: * AlterConfigsRequest * AlterUserScramCredentialsRequest * ExpireDelegationTokenRequest * IncrementalAlterConfigsRequest * RenewDelegationTokenRequest * SaslAuthenticateRequest * createDelegationTokenResponse * describeDelegationTokenResponse * SaslAuthenticateResponse This issue affects Apache Kafka: from any version supported the listed API above through v3.9.1, v4.0.0. We advise the Kafka users to upgrade to v3.9.2, v4.0.1, or later to avoid this vulnerability.

Published Apr 20, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: apache

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.9% (30-day exploitation probability)+9
Technical severity (medium)+3
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.89%

ahead of 58% of scored CVEs · Oct 14, 2026

Affects

Apache Software Foundation

Apache Kafka Clients and 1 more

CVSS base

5.3

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented mitigation — lists.apache.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Apache Kafka Clients, Apache Software Foundation Kafka).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
Apply the documented mitigations until a definitive fix is available.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Apache Software Foundation	Apache Kafka Clients	≥ 0.11.0 and ≤ 3.9.1version 4.0.0	Vulnerable	CVE Program (cve.org) e CISA ADP
Apache Software Foundation	Kafka	≥ 0.11.0.0 and < 3.9.2version 4.0.0version 4.0.0-rc0version 4.0.0-rc1version 4.0.0-rc3	Vulnerable	NIST National Vulnerability Database
Apache Software Foundation	Kafka	≥ 0.11.0 and ≤ 3.9.1version 4.0.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.3	CVSS 3.1	Medium	3.9	1.4	134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
5.3	CVSS 3.1	Medium	—	—	CISA-ADP via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N (score shown at the top: 134c704f-9b21-4f2e-91b3-4a467353bcc0)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-533

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.89%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · apache software foundation/apache kafka, apache software foundation/apache kafka clients
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 5.3
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 20, 2026 · apache

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

3 on the record

kafka.apache.org/cve-list
Vendor Advisory, vendor-advisory, NIST National Vulnerability Database
lists.apache.org/thread/pz5g4ky3h0k91tfd14p0dzqjp80960kl
Mitigation, Vendor Advisory, mailing-list, NIST National Vulnerability Database
www.openwall.com/lists/oss-security/2026/04/17/3
Mailing List, NIST National Vulnerability Database

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor

CWE-533
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-41115 Apache Kafka: Improper Authorization in CONSUMER_GROUP_DESCRIBE API Jun 2, 2026
Critical CVE-2026-33557 Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication Apr 20, 2026
High CVE-2026-35554 Apache Kafka Clients: Kafka Producer Message Corruption and Misrouting via Buffer Pool Race Condition Apr 7, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-33558 is "Apache Kafka, Apache Kafka Clients: Information Exposure Through Network Client Log Output", rated Medium. It affects Apache Kafka Clients (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.3 describes technical severity. EPSS 0.89% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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