CVE-2026-84501
Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider
At a glance
- Source
- NVD
- EPSS
- EPSS 0.74 % · percentile 55 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- apache
- NVD status
- Analyzed
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.
Weaknesses (CWE)
- CWE-117 — Improper Output Neutralization for Logs
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | CISA-ADP |
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | NVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
European references
- ENISA EUVD · EUVD-2026-80334
- GCVE · GCVE-0-2026-84501
CERT-FR advisories
- CERTFR-2026-AVI-1177 — Multiples vulnérabilités dans Apache Zookeeper · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*≥ 3.8.0 < 3.8.7cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*≥ 3.9.0 < 3.9.6
Affected products
| Product | Versions |
|---|---|
| Apache Software Foundation · Apache ZooKeeper | affected 3.9.0 ≤ 3.9.5 ; affected 3.8.0 ≤ 3.8.6 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |