CVE-2026-84501
Description
A flaw was found in Apache ZooKeeper. An unauthenticated attacker can inject arbitrary fake log lines into the operational log by sending a specially crafted request containing newline characters. This vulnerability allows the attacker to forge complete log entries, including timestamps, log levels, and messages. These forged entries are visually indistinguishable from genuine ZooKeeper log output, which could lead to misinterpretation of system activity and hinder incident response efforts.
Statement
A flaw was found in Apache ZooKeeper. Operational log entries can be forged via newline injection in ensemble authentication requests, allowing unauthenticated attackers to inject arbitrary log records. This may obscure malicious activity or create false audit trails. This issue affects Apache ZooKeeper versions 3.8.0 through 3.8.6 and 3.9.0 through 3.9.5.
Mitigation
Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 5.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability,Non-Repudiation
Technical Impact: Modify Application Data; Hide Activities; Execute Unauthorized Code or Commands
Interpretation of the log files may be hindered or misdirected if an attacker can supply data to the application that is subsequently logged verbatim. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. Forged or otherwise corrupted log files can be used to cover an attacker's tracks, possibly by skewing statistics, or even to implicate another party in the commission of a malicious act. If the log file is processed automatically, the attacker can render the file unusable by corrupting the format of the file or injecting unexpected characters. An attacker may inject code or other commands into the log file and take advantage of a vulnerability in the log processing utility.
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