VYPR
← All advisories
Critical severityNVD Advisory· Published Oct 11, 2023· Updated Apr 23, 2025

Apache ZooKeeper: Authorization bypass in SASL Quorum Peer Authentication

CVE-2023-44981

Description

Authorization Bypass Through User-Controlled Key vulnerability in Apache ZooKeeper. If SASL Quorum Peer authentication is enabled in ZooKeeper (quorum.auth.enableSasl=true), the authorization is done by verifying that the instance part in SASL authentication ID is listed in zoo.cfg server list. The instance part in SASL auth ID is optional and if it's missing, like 'eve@EXAMPLE.COM', the authorization check will be skipped. As a result an arbitrary endpoint could join the cluster and begin propagating counterfeit changes to the leader, essentially giving it complete read-write access to the data tree. Quorum Peer authentication is not enabled by default.

Users are recommended to upgrade to version 3.9.1, 3.8.3, 3.7.2, which fixes the issue.

Alternately ensure the ensemble election/quorum communication is protected by a firewall as this will mitigate the issue.

See the documentation for more details on correct cluster administration.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Apache ZooKeeper's SASL Quorum Peer authentication can be bypassed when the instance part of the SASL auth ID is omitted, allowing an arbitrary endpoint to join the cluster with full read-write access.

Vulnerability

Overview

CVE-2023-44981 is an authorization bypass vulnerability in Apache ZooKeeper's SASL Quorum Peer authentication mechanism. When SASL Quorum Peer authentication is enabled (via quorum.auth.enableSasl=true), the authorization check verifies that the instance part of the SASL authentication ID is present in the server list defined in zoo.cfg. However, because the instance part is optional, an attacker can supply an SASL auth ID such as eve@EXAMPLE.COM (with no instance part), which causes the authorization check to be skipped entirely. This allows an unauthenticated endpoint to join the cluster [1][2].

Exploitation

An attacker can exploit this by providing a crafted SASL authentication ID that lacks the instance part. Since the authorization check is bypassed, the attacker's endpoint can join the ZooKeeper ensemble. The vulnerability requires that SASL Quorum Peer authentication be enabled, which is not the default configuration. However, in environments where this is enabled, an attacker with network access to the ZooKeeper cluster can exploit the flaw without any prior authentication [1][2].

Impact

A successful attack allows the malicious endpoint to propagate counterfeit changes to the leader, effectively granting the attacker complete read-write access to the entire data tree managed by ZooKeeper. This can lead to data integrity breaches, unauthorized modification of configuration data, and potential disruption of services that rely on ZooKeeper for coordination [1][2].

Mitigation

The vulnerability has been fixed in Apache ZooKeeper versions 3.9.1, 3.8.3, and 3.7.2. Users are strongly recommended to upgrade to one of these patched versions. As an interim mitigation, administrators can protect ensemble election and quorum communication using a firewall to restrict network access, which reduces the attack surface [1][2].

References
  1. NVD - CVE-2023-44981
  2. security - CVE-2023-44981: Apache ZooKeeper: Authorization bypass in SASL Quorum Peer Authentication

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
org.apache.zookeeper:zookeeperMaven
< 3.7.23.7.2
org.apache.zookeeper:zookeeperMaven
>= 3.8.0, < 3.8.33.8.3
org.apache.zookeeper:zookeeperMaven
>= 3.9.0, < 3.9.13.9.1

Affected products

123

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

8

News mentions

0

No linked articles in our index yet.