Skip to main content

Unbound EUVDEUVD-2026-31084

| CVE-2026-42959 HIGH
Access of Uninitialized Pointer (CWE-824)
2026-05-20 sep@nlnetlabs.nl GHSA-5jp8-75xr-qrmf
Memory Corruption Denial Of Service Unbound
8.7
CVSS 4.0 · Vendor: nlnetlabs
Share

Severity by source

Vendor (nlnetlabs) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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:Red
SUSE
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (nlnetlabs).

CVSS VectorVendor: nlnetlabs

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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:Red
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

2
Patch available
May 20, 2026 - 11:02 EUVD
Analysis Generated
May 20, 2026 - 10:30 vuln.today

DescriptionCVE.org

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

AnalysisAI

Remote denial of service in NLnet Labs Unbound recursive DNS resolver (versions up to and including 1.25.0) allows an attacker controlling a DNSSEC-signed domain to crash the resolver process with a single crafted query. The DNSSEC validator uses an incorrect counter when computing write offsets for ADDITIONAL section rrsets while building chase-reply messages, leaving an uninitialized pointer that is later dereferenced. No public exploit identified at time of analysis, and the issue is fixed in Unbound 1.25.1.

More in Unbound

View all
CVE-2019-18934 HIGH POC
7.3 Nov 19

Unbound 1.6.4 through 1.9.4 contain a vulnerability in the ipsec module that can cause shell code execution after receiv
CVE-2026-33278 CRITICAL
9.1 May 20

Use-after-free in the DNSSEC validator of NLnet Labs Unbound resolver versions 1.19.1 through 1.25.0 allows remote attac
CVE-2026-42944 HIGH
8.7 May 20

Heap overflow denial-of-service in NLnet Labs Unbound recursive DNS resolver versions 1.14.0 through 1.25.0 allows remot
CVE-2022-3204 HIGH
7.5 Sep 26

A vulnerability named 'Non-Responsive Delegation Attack' (NRDelegation Attack) has been discovered in various DNS resolv
CVE-2020-10772 HIGH
7.5 Nov 27

An incomplete fix for CVE-2020-12662 was shipped for Unbound in Red Hat Enterprise Linux 7, as part of erratum RHSA-2020
CVE-2020-12663 HIGH
7.5 May 19

Unbound before 1.10.1 has an infinite loop via malformed DNS answers received from upstream servers. Rated high severity
CVE-2020-12662 HIGH
7.5 May 19

Unbound before 1.10.1 has Insufficient Control of Network Message Volume, aka an "NXNSAttack" issue. Rated high severity
CVE-2019-16866 HIGH
7.5 Oct 03

Unbound before 1.9.4 accesses uninitialized memory, which allows remote attackers to trigger a crash via a crafted NOTIF
CVE-2024-1488 HIGH
7.3 Feb 15

A vulnerability was found in Unbound due to incorrect default permissions, allowing any process outside the unbound grou
CVE-2026-42534 MEDIUM
6.9 May 20

Resolution performance degradation in NLnet Labs Unbound 1.25.0 and earlier allows an unauthenticated remote attacker -

CVE-2026-44390 MEDIUM
6.9 May 20

Denial of service in NLnet Labs Unbound 1.25.0 and earlier allows remote unauthenticated attackers to exhaust CPU resour
CVE-2026-41292 MEDIUM
6.6 May 20

Unbound DNS resolver versions up to and including 1.25.0 allow remote unauthenticated attackers to degrade or deny servi

Same weakness CWE-824 – Access of Uninitialized Pointer

View all
CVE-2015-1770 HIGH
8.8
CVE-2016-4343 HIGH POC
8.8
CVE-2020-25573 CRITICAL POC
9.8
CVE-2018-11743 CRITICAL POC
9.8
CVE-2018-9948 MEDIUM POC
6.5
CVE-2018-19857 CRITICAL POC
9.1
CVE-2018-3842 HIGH POC
8.8
CVE-2018-16522 HIGH POC
8.1

Same technique Memory Corruption

View all
CVE-2015-5119 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
9.8
CVE-2011-2462 CRITICAL POC
9.8
CVE-2011-0611 HIGH POC
8.8
CVE-2014-0322 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8
CVE-2012-4792 HIGH POC
8.8
CVE-2010-3333 HIGH POC
7.8

Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected
SUSE Linux Enterprise Micro 5.5 Affected

Share

EUVD-2026-31084 vulnerability details – vuln.today
Back

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy