Bug 2535097 (CVE-2026-59969)

Summary: CVE-2026-59969 zookeeper: Apache ZooKeeper: Improper certificate validation in FIPS mode allows quorum compromise
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anujha, asoldano, asyoung, ataylor, bbaranow, bmaxwell, bstansbe, csuconic, dbruscin, dlofthou, eglynn, ehugonne, fmariani, fmongiar, gmalinko, gtully, istudens, ivassile, iweiss, janstey, jhollowa, jjoyce, jnethert, jpretori, jschluet, jsherman, jwon, kaycoth, kvanderr, lhh, mburns, mcarlett, mgarciac, mosmerov, msvehla, nwallace, pberan, pdelbell, pesilva, pjindal, pmackay, prichard, rgemmell, rgodfrey, rstancel, rstepani, sthirugn, tbish, tcunning, thjenkin, tlavocat, vdosoudi, yfang
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Apache ZooKeeper. When operating in FIPS (Federal Information Processing Standards) mode with specific Transport Layer Security (TLS) settings enabled, ZooKeeper's quorum communication fails to properly verify the hostname of peer certificates. This vulnerability allows a malicious actor, using a specially crafted or misissued certificate, to join the ZooKeeper cluster. Such an actor could then participate in critical operations like leader election and data replication, potentially leading to unauthorized access or disruption of the ZooKeeper service.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2542323, 2542324, 2542325    
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Description OSIDB Bzimport 2026-09-16 09:49:46 UTC 
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.