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CVE-2026-84501 Apache ZooKeeper

Affected softwareApache ZooKeeper
Severity5.3 Medium CVSS 3.1
WeaknessCWE-117
Published16 Sep 2026
Updated18 Sep 2026

Published 59 days ago. NVD often adds the list of affected products days or weeks after a CVE is published, and the other sources we check lag too. The scope and status here may change.

Description

An unauthenticated attacker can inject arbitrary fake log lines into Apache ZooKeeper's operational log by sending a crafted add_auth("ensemble", ...) request containing newline characters (\n). When the ensemble name doesn't match, EnsembleAuthenticationProvider.handleAuthentication() logs the raw, unsanitized name via LOG.warn(). Because SLF4J's {} placeholder preserves embedded newlines, the attacker can forge complete log entries — with arbitrary timestamps, log levels, class names, and messages — that are visually indistinguishable from genuine ZooKeeper log output. This issue affects Apache ZooKeeper: from 3.9.0 through 3.9.5, from 3.8.0 through 3.8.6. Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC none indexed
  • EPSS 0.74% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

VRT has not found a public code change for this CVE yet.

  • Protection none
  • Action not pursued
  • Review automated Upstream data
  • Record active
Decided by Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read
Finding This CVE affects a known product, but nothing published names a fix and nothing published shows an exploit. That is a statement about the evidence, not about the defect — it does not mean the vulnerability is unimportant or unreachable, only that neither of the two things VRT can act on exists.

Affected software and releases

Oracle advisories

AdvisoryTypeQuarterProducts Oracle names in its risk matrix
Oracle Critical Patch Update October 2026 ↗ CPU 2026-Q4 Oracle Construction and Engineering / Platform (Apache ZooKeeper) (21.12.0-21.12.17, 22.12.0-22.12.15, 23.12.0-23.12.16, 24.12.0-24.12.16, 25.12.0-25.12.9)

Oracle components and versions

FamilyComponentVersions, as Oracle lists themRead as
Oracle Construction and Engineering Platform (Apache ZooKeeper) 21.12.0-21.12.17, 22.12.0-22.12.15, 23.12.0-23.12.16, 24.12.0-24.12.16, 25.12.0-25.12.9

Products and versions

1 product, 2 version entries
SourceVendorProductSchemeAffected versions
nvd apache zookeeper generic ≥ 3.8.0 and < 3.8.7 · ≥ 3.9.0 and < 3.9.6

References

URLTags
https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y Mailing List, Vendor Advisory
http://www.openwall.com/lists/oss-security/2026/09/15/7 Mailing List

Timeline

Published2026-09-16By the CVE Program.
NVD record modified2026-09-18NVD's own last-modified date for this record.