CVE-2026-42534: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-xfcv-gp55-3wpf
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CVSS 5.3
CWE-440 CWE-911
Published
Advisory Summary

CVE-2026-42534 is a MODERATE (CVSS 5.3) security vulnerability vulnerability (CWE-440: Expected Behavior Violation) affecting Software libraries in the Maven ecosystem. The weakness occurs when a feature, api, or function does not perform according to its specification.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-42534 at a Glance

CVE Identifier CVE-2026-42534
GHSA Identifier GHSA-xfcv-gp55-3wpf
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-440: Expected Behavior Violation
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix CVE-2026-42534

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-42534, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-440: Expected Behavior Violation, where a feature, api, or function does not perform according to its specification. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.

References

NVD — CVE-2026-42534 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42534
access.redhat.com/errata/rhsa-2026:24... WEB
https://access.redhat.com/errata/RHSA-2026:24013
access.redhat.com/errata/rhsa-2026:36... WEB
https://access.redhat.com/errata/RHSA-2026:36320
access.redhat.com/errata/rhsa-2026:36... WEB
https://access.redhat.com/errata/RHSA-2026:36777
access.redhat.com/errata/rhsa-2026:37... WEB
https://access.redhat.com/errata/RHSA-2026:37282
Software Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-42534
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2480131
Software Security Information SECURITY
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42534.json
www.nlnetlabs.nl/downloads/unbound/c... WEB
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txt

Frequently Asked Questions

What is CVE-2026-42534?
CVE-2026-42534 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-440: Expected Behavior Violation.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-42534?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-42534?
CVE-2026-42534 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-42534?
CVE-2026-42534 is classified under CWE-440: Expected Behavior Violation (A feature, API, or function does not perform according to its specification.).
How can I check Maven dependencies for CVE-2026-42534?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xfcv-gp55-3wpf",
  "modified" : "2026-07-29T15:30:48Z",
  "published" : "2026-05-20T12:30:36Z",
  "aliases" : [ "CVE-2026-42534" ],
  "details" : "NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42534"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:24013"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:36320"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:36777"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:37282"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-42534"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2480131"
  }, {
    "type" : "WEB",
    "url" : "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42534.json"
  }, {
    "type" : "WEB",
    "url" : "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txt"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-440", "CWE-911" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-05-20T10:16:27Z"
  }
}