CVE-2026-42944Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
Updated under an hour ago ()
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It affects NLnet Labs Unbound and 3 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 8.7 HIGH (v4.0, CNA)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/U:Red
- Weakness (CWE)
- CWE-197, CWE-787, CWE-131
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- NLnet Labs
- NVD analysis
- Modified
- Record last updated
- Aug 26, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
NLnet Labs Unbound nlnet_labs:unbound (from the name) | from 1.14.0 before 1.25.1 | CNA record |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | from 0:1.24.2-7.el10_2.1 not affected | CISA ADP |
Red Hat Red Hat Hardened Images redhat:hummingbird | from 1.25.1-0.1.hum1 not affected | CISA ADP |
nlnetlabs unbound nlnetlabs:unbound | from 1.14.0 before 1.25.1 | NVD |
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txtvendor-advisory, mitigation
- https://access.redhat.com/errata/RHSA-2026:19752
- https://access.redhat.com/errata/RHSA-2026:23231
- https://access.redhat.com/errata/RHSA-2026:24365
- https://access.redhat.com/errata/RHSA-2026:24369
- https://access.redhat.com/security/cve/CVE-2026-42944
- https://bugzilla.redhat.com/show_bug.cgi?id=2479774
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42944.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.