Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:NSummary
CVE-2026-24281 is a high-severity Improper Certificate Validation (CWE-295) vulnerability in Apache Zookeeper. Its CVSS base score is 7.4 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 47th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to IA-3 (Device Identification and Authentication) and SC-17 (Public Key Infrastructure Certificates) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-24281 is a vulnerability in the hostname verification logic of Apache ZooKeeper's ZKTrustManager component. When IP Subject Alternative Name (SAN) validation fails during TLS certificate checks, the implementation falls back to reverse DNS (PTR record) lookups. This affects Apache ZooKeeper versions prior to 3.8.6 and 3.9.5, enabling attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients if they possess a certificate trusted by the ZKTrustManager. The issue is classified under CWE-295 (Improper Certificate Validation) and CWE-350 (Reliance on Reverse DNS Resolution for a Security-Critical Action), with a CVSS v3.1 base score of 7.4 (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).
An attacker can exploit this over the network with high attack complexity and no privileges or user interaction required. Exploitation requires the adversary to spoof or control the PTR record for the target's IP address and present a valid, trusted certificate matching the PTR-resolved hostname. Successful exploitation allows impersonation of legitimate ZooKeeper servers or clients, potentially leading to high confidentiality and integrity impacts, such as unauthorized access to ZooKeeper ensembles or man-in-the-middle attacks on client-quorum communications.
Apache advisories recommend upgrading to ZooKeeper 3.8.6 or 3.9.5, which address the issue by introducing a new configuration option to disable reverse DNS lookups in client and quorum protocols. Details are available in the Apache mailing list announcement at https://lists.apache.org/thread/088ddsbrzhd5lxzbqf5n24yg0mwh9jt2 and the oss-security mailing list at http://www.openwall.com/lists/oss-security/2026/03/07/4.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-10139
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 12 hardening rules · 3 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Requiring unique device identification and authentication before any connection prevents security decisions based solely on unverified reverse DNS lookups.
PKI certificate issuance and acquisition under an approved policy establishes the trusted roots and processes needed for correct validation.
Mandating data-origin authentication for name/address resolution stops reliance on unauthenticated reverse DNS responses.
Protecting session authenticity depends on cryptographic mechanisms whose trust depends on correct certificate validation.
Requiring confidentiality and integrity protection of transmitted data drives use of properly validated certificates in protocols such as TLS.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Certificate-based authentication of users/services/hardware directly depends on correct validation.
Proper certificate validation is a core mechanism for protecting data-in-transit confidentiality and integrity.
Secure development practices explicitly include implementing correct certificate validation logic.
Monitoring DNS services can detect adverse events stemming from unverified reverse lookups.
Assessing authenticity/integrity of acquired software often relies on code-signing certificate validation.
Identity assertions conveyed via certificates require validation to be verified.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Network security controls can enforce authenticated, non-DNS-based host identification.
Secure network services discourage use of unauthenticated reverse-DNS for access decisions.
Requiring issuance and validation of public-key certificates under an approved policy reduces the chance that certificates with improper validation will be trusted.
Application security requirements can mandate authenticated host verification instead of reverse DNS.
Secure architecture principles discourage reliance on unauthenticated DNS for security decisions.
Secure coding practices can replace reverse-DNS checks with cryptographically verified identities.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (3 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-295
- V-248531 OL 8, for PKI-based authentication, must validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor. prevents CWE-295
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
RHEL 7 (2 rules)
- V-204447 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
- V-204448 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
RHEL 8 (2 rules)
- V-230264 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295