Apache ZooKeeper: Improper Certificate Validation
CVE-2026-24281 is a high-severity improper certificate validation vulnerability in Apache ZooKeeper from Apache, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache ZooKeeper versions: 3.9.0 through 3.9.4; 3.8.0 through 3.8.5. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.69% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Zookeeper to 3.8.6 or 3.9.5, whichever matches your release line, or a later version.
- Read the advisory on lists.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache ZooKeeper | 3.9.0 through 3.9.4; 3.8.0 through 3.8.5 | Not stated |
| Red Hat | Red Hat AMQ Broker 7.12.7 | Not specified in the record | Not stated |
| Red Hat | Red Hat AMQ Broker 7.13.5 | Not specified in the record | Not stated |
| Red Hat | Red Hat AMQ Broker 7.14.0 | Not specified in the record | Not stated |
| Red Hat | Streams for Apache Kafka 2.9.4 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI 2.25 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Debezium 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Debezium 3 | Not specified in the record | Not stated |
| Red Hat | Red Hat Data Grid 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Fuse 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | Not specified in the record | Not stated |
| Red Hat | Red Hat Offline Knowledge Portal | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI (RHOAI) | Not specified in the record | Not stated |
| Red Hat | streams for Apache Kafka 3 | Not specified in the record | Not stated |
| Apache | Zookeeper | 3.8.0 up to, but not including, 3.8.6; 3.9.0 up to, but not including, 3.9.5 | 3.8.6, 3.9.5 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.4 | High | NVD |
| CVSS 3.1 | 5.9 | Medium | CISA (ADP) |
| CVSS 3.1 | 7.4 | High | CNA |
Official description
Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name. It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.
How developers prevent this class of flaw
- Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
- If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
More Improper Certificate Validation vulnerabilities (CWE-295)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- openwall.com/lists/oss-security/2026/03/07/4Mailing List, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:10184
- access.redhat.com/errata/RHSA-2026:14272
- access.redhat.com/errata/RHSA-2026:14276
- access.redhat.com/errata/RHSA-2026:34608
- access.redhat.com/errata/RHSA-2026:8509
- access.redhat.com/security/cve/CVE-2026-24281
- bugzilla.redhat.com/show_bug.cgi?id=2445449
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-24281.json
Other vulnerabilities in Apache ZooKeeper
- 8.7 High severity
- 7.1 High severity
- 8.7 High severity
- 8.6 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Certificate Validation vulnerabilities
- 8.8 High severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 7.4 High severity
- 7.4 High severity
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