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TI-2026-25690 Aliases CVE-2026-33278GHSA-m234-r435-cxjw

Possible arbitrary code execution during DNSSEC validation

Priority MEDIUM 50CWE-416Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 5 fixed, 3 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0142 72nd percentileScored 2026-11-07
Fix Partial Unbound (NLnet Labs): 1.25.1Red Hat: 3 advisoriesRed Hat: 5 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
NLnet LabsUnbound1.19.1 to before 1.25.11.25.1Patch availableCNA
  • Unbound VendorNLnet Labs Affected 1.19.1 to before 1.25.1 Fixed in 1.25.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*1.19.1 to before 1.25.1VulnerableNLNETLABS
  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions 1.19.1 to before 1.25.1 Vulnerable ·NLNETLABS

Remediation

  • Fix · CNA Unbound (NLnet Labs) Fixed in 1.25.1

Red Hat 3 advisories

  • RHSA-2026:24369 Released 2026-06-08 · Red Hat rating Important
    unbound security update
    • Red Hat Enterprise Linux AppStream (v. 9) python3-unbound-1.24.2-3.el9_8.1, unbound-1.24.2-3.el9_8.1, unbound-dracut-1.24.2-3.el9_8.1 +1
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) unbound-devel-1.24.2-3.el9_8.1
  • RHSA-2026:23231 Released 2026-06-04 · Red Hat rating Important
    unbound security update
    • Red Hat Enterprise Linux AppStream (v. 10) python3-unbound-1.24.2-7.el10_2.1, unbound-1.24.2-7.el10_2.1, unbound-anchor-1.24.2-7.el10_2.1 +3
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) unbound-devel-1.24.2-7.el10_2.1
  • RHSA-2026:19752 Released 2026-05-20 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images python3-unbound-1.25.1-0.1.hum1@aarch64, python3-unbound-1.25.1-0.1.hum1@x86_64, unbound-1.25.1-0.1.hum1@aarch64 +14

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    NLnet Labs Unbound 1.25.1

    11 records Highest priority Priority MEDIUM 3 MEDIUM, 8 LOW

    Other records, highest priority first

    • TI-2026-31146 Crash during DNSSEC validation of malicious contentPriority MEDIUM 45
    • TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS optionsPriority MEDIUM 45
    • TI-2026-32341 Unbounded name compression in certain cases causes degradation of servicePriority LOW 37
    Show all 11 records →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat OpenShift Container Platform 4Affected—
Red Hat OpenShift Container Platform 5Affected—
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:23231
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:24369
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:23231
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:24369
Red Hat Hardened ImagesFixed RHSA-2026:19752
Not affected: 3 products
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-33278
  2. 2026-10-03 Alias added: GHSA-m234-r435-cxjw
  3. 2026-10-30 Affected versions changed · Red Hat

References

Advisory 1

  • TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY CVSS 4.0CRITICAL 9.1
  • TI-2026-31146 Crash during DNSSEC validation of malicious content CVSS 4.0HIGH 8.7
  • TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options CVSS 4.0HIGH 8.7
  • TI-2026-36436 Routinator crashes on specifically crafted RRDP XML files CVSS 4.0HIGH 8.7
  • TI-2026-36433 Routinator exits when accepting an incoming HTTP or RTR connection fails CVSS 4.0HIGH 8.7
  • TI-2026-10532 Denial of DNS over TLS service by any DoT client CVSS 4.0HIGH 8.7
See all 96 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences