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VulnerabilityPublished

CVE-2026-100302: Apache ZooKeeper · Unthrottled Resource Allocation

Affects Apache ZooKeeperSource CVE Database V5

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Not known to be exploited · CVSS 7.1 High · fixed in 3.9.7 : patch Apache ZooKeeper soon.

Data as of 4 Nov 2026, 11:43 UTC

CVSS 4.0 base score
7.1High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (apache)CVSS 4.07.1
Patch
Available – fixed in 3.9.7
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 4 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 4 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Apache ZooKeeperorg.apache.zookeeper:zookeeperAffected
  • >=3.9.0 <=3.9.6
  • >=3.8.0 <=3.8.7
Fixed in–
Mavenorg.apache.zookeeper/zookeeperpkg:maven/org.apache.zookeeper/zookeeperOther threatsAffected
  • >=3.9.0 <=3.9.6
  • >=3.8.0 <=3.8.7
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should upgrade Apache ZooKeeper to version 3.9.7 or later, where configurable limits on the multiRead operation count and cumulative response size have been implemented to prevent resource exhaustion. No other mitigations are indicated or effective, as existing request size limits do not constrain the response size. Applying the official fix is the recommended remediation.

Description

Allocation of Resources Without Limits or Throttling in the multiRead request handler of Apache ZooKeeper allows a remote attacker to crash the server (denial of service) with a single small request. The multiRead handler places no limit on the number of bundled read operations or on the cumulative size of the response it builds in memory. Because each operation's result is fully materialized and retained before serialization, a request that is small on the wire — within the jute.maxbuffer limit — but that references a large znode many times can force the server to allocate far more heap than the request size implies, exhausting the JVM heap and terminating the server with an OutOfMemoryError. Neither jute.maxbuffer nor largeRequestMaxBytes prevents this, as both bound only the inbound request, not the response. This issue affects Apache ZooKeeper from 3.7.0 through 3.9.6. Users are recommended to upgrade to version 3.9.7, which enforces configurable limits on the multiRead operation count and cumulative response size.

References

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