How severe is CVE-2026-59969?

CVE-2026-59969 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-59969 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-59969?

CVE-2026-59969 affects Apache Zookeeper. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-59969?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-59969 published?

CVE-2026-59969 was published on 2026-09-16 and last updated on 2026-09-18.

CVE-2026-59969

CVE-2026-59969 is a high-severity vulnerability in Apache Zookeeper with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-297.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (24th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-297
Affected product: Apache Zookeeper
Published: 2026-09-16
Last modified: 2026-09-18

Description

Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments. When sslQuorum=true, zookeeper.fips-mode=true, ssl.quorum.hostnameVerification=true, and ssl.quorum.clientHostnameVerification=true are enabled, the Java SSLSocket quorum path accepts a CA-trusted peer certificate whose SAN does not match the connected host. A malicious or misissued peer certificate can therefore join quorum traffic, participate in leader election, and enter replication flows. Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.

Frequently asked questions

What is CVE-2026-59969?: Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments. When sslQuorum=true, zookeeper.fips-mode=true, ssl.quorum.hostnameVerification=true, and ssl.quorum.clientHostnameVerification=true are enabled, the Java SSLSocket quorum path accepts a CA-trusted peer certificate whose SAN does not match the connected host. A malicious or misissued peer certificate can therefore join quorum traffic, participate in leader election, and enter replication flows. Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.
How severe is CVE-2026-59969?: CVE-2026-59969 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-59969 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-59969?: CVE-2026-59969 affects Apache Zookeeper. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-59969?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-59969 published?: CVE-2026-59969 was published on 2026-09-16 and last updated on 2026-09-18.

References

Affected products (1)

cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*

More vulnerabilities in Apache Zookeeper

CVE-2024-51504 — Critical (CVSS 9.1): When using IPAuthenticationProvider in ZooKeeper Admin Server there is a possibility of Authentication Bypass by…
CVE-2023-44981 — Critical (CVSS 9.1): Authorization Bypass Through User-Controlled Key vulnerability in Apache ZooKeeper. If SASL Quorum Peer authentication…
CVE-2016-5017 — High (CVSS 8.1): Buffer overflow in the C cli shell in Apache Zookeeper before 3.4.9 and 3.5.x before 3.5.3, when using the "cmd:" batch…
CVE-2026-79993 — High (CVSS 7.5): The `deleteContainer` opcode (0x14/20) is processed without verifying the caller's ACL permissions, allowing any…
CVE-2026-59739 — High (CVSS 7.5): Information disclosure via SetWatches reconnect replay in Apache ZooKeeper due to missing ACL check. An attacker can…
CVE-2026-24308 — High (CVSS 7.5): Improper handling of configuration values in ZKConfig in Apache ZooKeeper 3.8.5 and 3.9.4 on all platforms allows an…

All CVEs affecting Apache Zookeeper →

Other CWE-297 vulnerabilities

CVE-2025-46408 — Critical (CVSS 9.8): An issue was discovered in the methods push.lite.avtech.com.AvtechLib.GetHttpsResponse and…
CVE-2026-15925 — Critical (CVSS 9.2): Improper TLS hostname verification in Snowflake Connector for Python versions prior to 4.7.1 and 3.18.1 may have…
CVE-2026-48144 — Critical (CVSS 9.1): Improper Validation of Certificate with Host Mismatch vulnerability in Apache Thrift c_glib bindings. This issue…
CVE-2025-68637 — Critical (CVSS 9.1): The Uniffle HTTP client is configured to trust all SSL certificates and disables hostname verification by default.…
CVE-2026-35563 — High (CVSS 8.5): It was identified that the LDAP client implementation in version 2.1.7 does not verify if the server certificate…
CVE-2025-3501 — High (CVSS 8.2): A flaw was found in Keycloak. By setting a verification policy to 'ALL', the trust store certificate verification is…

Browse all CWE-297 vulnerabilities →