Vulnerability in kafka (CVE-2026-33557)
Summary
Vulnerability in kafka (CVE-2026-33557). Confidential information can be exposed externally. Exploitable via sasl.oauthbearer.jwt.validator.class. Mitigation: upgrade to 4.1.2 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-33557 has been found in kafka.
Attackers can target a specific entry point like sasl.oauthbearer.jwt.validator.class over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: upgrade kafka to 4.1.2 or later.
If unsure, ask your IT team or search "kafka CVE-2026-33557" on the vendor's site.
CVE-2026-33557 (kafka) — CWE-1285 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: sasl.oauthbearer.jwt.validator.class / preferred_username
Patched: 4.1.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-1285) exists in kafka. Attackers reach the vulnerable code path via sasl.oauthbearer.jwt.validator.class without authentication.
Check the vendor advisory for the affected versions of kafka. Attack surface: sasl.oauthbearer.jwt.validator.class / preferred_username.
Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.
Update to 4.1.2.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'kafka' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'kafka' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
kafkaを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade kafka to 4.1.2ステージング環境で 4.1.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-33557 kafka
References
- advisory kafka.apache.org
- advisory access.redhat.com
- advisory nvd.nist.gov
- advisory github.com
- report bugzilla.redhat.com
- web lists.apache.org
- web openwall.com
- web security.access.redhat.com