CVE-2026-59969: apache software foundation apache zookeeper
Vulnerability summary
CVE-2026-59969 is a high (CVSS 7.5) vulnerability in apache software foundation apache zookeeper. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 24.5% of scored vulnerabilities.
Timeline
- 16-09-2026PublishedVulnerability first disclosed.
- 17-09-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
0.33%
Chance of exploitation in the next 30 days
Percentile
25%
Versus all other CVEs
30-day change
+0.07 pp
From 0.26% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Apache1 product
- zookeeper≥ 3.8.0, < 3.8.7 | ≥ 3.9.0, < 3.9.6
Apache software foundation1 product
- apache zookeeper≥ 3.9.0, ≤ 3.9.5 | ≥ 3.8.0, ≤ 3.8.6
Debian1 product
- zookeeperAll versions (No fix recorded) | < 3.9.6-1
Ubuntu1 product
- zookeeperAll versions (No fix recorded)
4 vendors · 4 products
