Home/CVE/NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when enco
CVE
CVE-2026-42944
NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when enco
NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query.
A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.
HIGH · CVSS 7.5
EPSS 0.0006
Schedule remediation
- SSVC automatable: yes - attacks can be scripted at scale
- CVSS base score ≥ 7.0
Sigma rules0
YARA rules0
Look this up elsewhere - one-click external pivots
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How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2026-42944, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
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ATT&CK techniques
1Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.
▤ Build a SIEM detection for these techniques⬡
Weakness Classification
CWE-197Numeric Truncation Error
CWE-787Out-of-bounds Write
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Affected Products & Versions
1nlnetlabs unbound>= 1.14.0 and < 1.25.1
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Fixed versions by distribution
19The package version that resolves this CVE on each Linux distribution, from the vendor’s published security data. fixed in shows a patched version exists; open means the package is listed as affected with no fix yet.
alpine edgeunbound fixed in 1.25.1-r0
oracle allpython3-unbound fixed in 0:1.16.2-5.11.el8_10
oracle allunbound open
oracle allunbound-devel fixed in 0:1.16.2-5.11.el8_10
oracle allunbound-libs open
rhel 8python3-unbound open
rhel 8unbound open
rhel 8unbound-devel fixed in 0:1.16.2-5.11.el8_10
rhel 8unbound-libs fixed in 0:1.16.2-5.11.el8_10
rhel 9python3-unbound open
rhel 9unbound open
rhel 9unbound-devel open
rhel 9unbound-dracut fixed in 0:1.24.2-3.el9_8.1
rhel 9unbound-libs open
suse sle15libunbound8 fixed in 0:1.20.0-150100.10.25.1
suse sle15unbound fixed in 0:1.20.0-150600.23.16.1
suse sle15unbound-anchor fixed in 0:1.20.0-150100.10.25.1
suse sle15unbound-devel fixed in 0:1.20.0-150100.10.25.1
suse sle15unbound-python fixed in 0:1.20.0-150600.23.16.1
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Scoring & Timeline
7.5
HIGH · CVSS v3.1 · [email protected]
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
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Vendor Advisories
11suse-csafSUSE-SU-2026:2369-1
suse-csafSUSE-SU-2026:2281-1
suse-csafopenSUSE-SU-2026:10903-1
suse-csafSUSE-SU-2026:21874-1
suse-csafSUSE-SU-2026:21913-1
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References & Sources
1Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.