# CVE-2026-24281: Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager > Attackers can bypass hostname verification in Apache ZooKeeper by spoofing reverse DNS records, potentially impersonating servers or clients. - **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 Mar 2026 - **Updated:** 15 Jul 2026 - **Also known as:** BIT-zookeeper-2026-24281, CLEANSTART-2026-AS23649, CLEANSTART-2026-UU38488, DEBIAN-CVE-2026-24281, ECHO-6fcc-5bac-4e91, GHSA-7xrh-hqfc-g7qr, MINI-27xw-8vjg-944g, MINI-37v7-9qwp-9fg3, MINI-5c2x-33cm-xrcg, MINI-6pmm-qvgm-c4m4, MINI-7fp3-fc2h-5q79, MINI-8pqr-hq5p-wm53, MINI-8rf9-54mc-rhx9, MINI-9h9j-h6pc-x58m, MINI-fv68-q9vg-8xxc, MINI-pghp-387v-7w4f, MINI-r269-prwq-g7f2, MINI-r4vr-h5fw-63mg, MINI-rrcc-52q2-pg8h, MINI-rxx6-qwxm-67xc, MINI-v538-hw96-ff42, MINI-vgrp-q6f5-q8h3, MINI-xhf8-4pfp-fphv, RHLW-2026-3837a83be413601a, RHLW-2026-67695bc80de4b2e2, ROOT-APP-MAVEN-CVE-2026-24281, UBUNTU-CVE-2026-24281 ## What is CVE-2026-24281? CVE-2026-24281 is a medium-severity vulnerability in Apache ZooKeeper, published on 7 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name. It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols. Weakness: CWE-350 (Reliance on Reverse DNS Resolution for a Security-Critical Action), CWE-295 (Improper Certificate Validation) ## Which versions are affected by CVE-2026-24281? 5 open source packages ship an affected version, including org.apache.zookeeper:zookeeper and zookeeper. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.zookeeper:zookeeper` | Maven | From 3.8.0 | 3.8.6 | | `org.apache.zookeeper:zookeeper` | Maven | From 3.8.0 | 3.8.6 | | `org.apache.zookeeper:zookeeper` | Maven | From 3.9.0 | 3.9.5 | | `org.apache.zookeeper:zookeeper` | Maven | From 3.9.0 | 3.9.5 | | `zookeeper` | Bitnami | From 3.8.0 | 3.8.6, 3.9.5 | Products: Apache Zookeeper. ## How do I fix CVE-2026-24281? Upgrade org.apache.zookeeper:zookeeper to a fixed version for your release line: 3.8.6 or 3.9.5. ## Is CVE-2026-24281 being exploited? There is no known exploitation of CVE-2026-24281 in the wild and no public exploit code. ## Other vulnerabilities in Apache ZooKeeper - [CVE-2024-51504](https://insights.sbomify.com/CVE-2024-51504/): Apache ZooKeeper: Authentication bypass with IP-based authentication in Admin Server (critical 9.1) - [CVE-2023-44981](https://insights.sbomify.com/CVE-2023-44981/): Apache ZooKeeper: Authorization bypass in SASL Quorum Peer Authentication (critical 9.1) - [CVE-2016-5017](https://insights.sbomify.com/CVE-2016-5017/): Memory corruption in n/a (high 8.1) - [CVE-2026-59739](https://insights.sbomify.com/CVE-2026-59739/): Apache ZooKeeper: Information disclosure via SetWatches reconnect replay (high 7.5) - [CVE-2026-59969](https://insights.sbomify.com/CVE-2026-59969/): Apache ZooKeeper: Improper validation of certificate with host mismatch in FIPS mode (high 7.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-24281 and fix it if it is affected. What it is: CVE-2026-24281 is a medium-severity vulnerability in Apache ZooKeeper, published on 7 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-24281 in the wild and no public exploit code. Affected packages and fixed versions: - org.apache.zookeeper:zookeeper (Maven): affected from 3.8.0; fixed in 3.8.6 - org.apache.zookeeper:zookeeper (Maven): affected from 3.8.0; fixed in 3.8.6 - org.apache.zookeeper:zookeeper (Maven): affected from 3.9.0; fixed in 3.9.5 - org.apache.zookeeper:zookeeper (Maven): affected from 3.9.0; fixed in 3.9.5 - zookeeper (Bitnami): affected from 3.8.0; fixed in 3.8.6, 3.9.5 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-24281/ (Markdown: https://insights.sbomify.com/CVE-2026-24281/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-24281 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-24281 - OSV: https://osv.dev/vulnerability/CVE-2026-24281 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-24281/ Summaries are generated and may contain mistakes; the official description above is the record.