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CVE Record

CVE-2026-24281: Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager

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.

HighCVSS 7.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

ZooKeeper may trust the wrong host when TLS hostname checks fall back to reverse DNS. An attacker with influence over PTR records and a certificate trusted by ZooKeeper could impersonate a server or client. The attack is harder than typical network spoofing but can expose confidential data and integrity.

Executive priority

Treat as a high-priority infrastructure patch for ZooKeeper environments carrying sensitive coordination data. Prioritize internet-adjacent, multi-tenant, or less-controlled DNS environments first. No evidence in the bundle supports emergency active-exploitation response.

Technical view

Apache ZooKeeper ZKTrustManager falls back to reverse DNS when IP SAN validation fails. If a trusted certificate matches the PTR-derived hostname, hostname verification can be bypassed. Apache recommends upgrading to 3.8.6 or 3.9.5, which add an option to disable reverse DNS lookup in client and quorum protocols.

Likely exposure

Exposure is most likely in ZooKeeper deployments using TLS hostname verification with IP-based connections, especially where reverse DNS can be controlled or spoofed. The bundle identifies Apache ZooKeeper 3.8.0 and 3.9.0, with fixes in 3.8.6 and 3.9.5.

Exploitation context

The provided sources do not show active exploitation, and KEV is false. Exploitation requires network positioning or DNS influence plus a certificate trusted by ZKTrustManager, making the attack high-complexity but serious for sensitive clusters.

Researcher notes

Focus validation on ZKTrustManager behavior when IP SAN validation fails and PTR resolution returns a trusted certificate name. Avoid assuming affected downstream products beyond cited Red Hat advisories. Evidence is sufficient for impact and fixed versions, but deployment-specific reachability depends on TLS, DNS, and trust-store design.

Mitigation direction

  • Upgrade Apache ZooKeeper to 3.8.6 or 3.9.5.
  • Disable reverse DNS lookup using the new client and quorum protocol option.
  • Inventory direct and transitive org.apache.zookeeper:zookeeper dependencies.
  • Review ZKTrustManager trust stores and remove unexpected trusted certificate authorities.
  • Check Red Hat errata for downstream package fixes if applicable.

Validation and detection

  • Confirm ZooKeeper server and client library versions across all clusters.
  • Check whether TLS hostname verification is enabled for client and quorum traffic.
  • Verify reverse DNS fallback is disabled after upgrading.
  • Review DNS and PTR record control around ZooKeeper network paths.
  • Validate downstream vendor package status against Red Hat advisories where used.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-295: Exact CWE lookup

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cwe · low confidence lookup

CWE-350: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-24281 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
3ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.4CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N2.25.2redhat-SADP
5.9CVSS 3.1MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N2.23.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.4High
CVSS 3.1 vector shape for CVE-2026-24281Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPApache ZooKeeper: Apache ZooKeeper: Impersonation of servers or clients via reverse DNS spoofing
other:Red Hat severity ratingcvssV3_1
  • 2026-03-07T09:00:57.868Z: Reported to Red Hat.
  • 2026-03-07T08:50:32.525Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Apache Software FoundationApache ZooKeeperorg.apache.zookeeper:zookeeper, 3.9.0, 3.8.0unaffected
Weakness

CWE details

CWE-295CWE-350

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-295 · source CWE mapping

Improper Certificate Validation

Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-350 · source CWE mapping

Reliance on Reverse DNS Resolution for a Security-Critical Action

Reliance on Reverse DNS Resolution for a Security-Critical Action represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs