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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache ZooKeeper | 3.9.0 – ≤ 3.9.5, 3.8.0 – ≤ 3.8.6 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | zookeeper | 3.9.6-1 | — |
| Debian 13 | zookeeper | No fix yet | — |
| Debian 12 | zookeeper | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | zookeeper | No fix yet | — |
| Ubuntu 26.04 LTS | zookeeper | No fix yet | — |
| Ubuntu 24.04 LTS | zookeeper | No fix yet | — |
| Ubuntu 22.04 LTS | zookeeper | No fix yet | — |
| Ubuntu 20.04 LTS | zookeeper | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | zookeeper | No fix yet | — |
| Ubuntu Pro 16.04 LTS | zookeeper | No fix yet | — |
| Ubuntu Pro 14.04 LTS | zookeeper | No fix yet | — |
Advisories 1
- WID-SEC-2026-3908 IBM SPSS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 3, 2026
References
- https://lists.apache.org/thread/qf9kwsgtgbgtvwls6f41281846xg0rss vendor-advisory