CVE catalog
CVE-2026-42959
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 c
- Severity
- High · CVSS 8.7
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 - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.81% · Oct 27, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | unbound | sid | 1.26.2-1 | fixed |
| Debian | unbound | forky | 1.26.2-1 | fixed |
| Debian | unbound | trixie | 1.22.0-2+deb13u3 | fixed |
| Debian | unbound | trixie-security | 1.26.2-0+deb13u1 | fixed |
| Debian | unbound | bookworm | 1.17.1-2+deb12u4 | vulnerable |
| Debian | unbound | bookworm-security | 1.17.1-2+deb12u3 | vulnerable |
| Cpe | unbound | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | libunbound-dev | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | libunbound8 | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | python3-unbound | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | unbound-anchor | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | unbound-host | Not reported | 1.19.2-1ubuntu3.8 | fixed |
| Cpe | unbound | Not reported | Not reported | vulnerable |
| Cpe | unbound | Not reported | 1.25.1 | fixed |
| Cpe | unbound | Not reported | 1.25.1 | fixed |
| Alpine | unbound | 3.22 | 1.25.2-r0 | fixed |
| Alpine | unbound | 3.23 | 1.25.2-r0 | fixed |
| Alpine | unbound | 3.24 | 1.25.1-r0 | fixed |
| Ubuntu | unbound | pro | 1.9.0-2ubuntu1 | vulnerable |
| Ubuntu | unbound | pro | 1.9.0-2ubuntu2 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.1 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.2 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.3 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.4 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.5 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.6 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.8 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.9 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.11 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.11+esm1 | fixed |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu3 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.1 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.2 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.3 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.4 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.5 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.7 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.8 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.10 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.11 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.12 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.13 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.14 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.15 | fixed |
| Ubuntu | unbound | 24.04 | 1.17.1-2 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.18.0-2ubuntu1 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.18.0-2ubuntu2 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.1-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.1 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.2 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.3 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.4 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.5 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.6 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.7 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.8 | fixed |
| Ubuntu | unbound | 25.10 | 1.22.0-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 25.10 | 1.22.0-2ubuntu1 | vulnerable |
| Ubuntu | unbound | 25.10 | 1.22.0-2ubuntu2 | vulnerable |
| Ubuntu | unbound | 25.10 | 1.22.0-2ubuntu2.1 | vulnerable |
| Ubuntu | unbound | 25.10 | 1.22.0-2ubuntu2.2 | vulnerable |
| Ubuntu | unbound | 25.10 | 1.22.0-2ubuntu2.3 | fixed |
| Ubuntu | unbound | 26.04 | 1.22.0-2ubuntu2 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.22.0-2ubuntu4 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu2 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu2.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | unbound | source | sid | 1.25.1-1 | not yet assigned | Not reported | [1137187] |
| Debian | unbound | source | forky | 1.25.1-1 | not yet assigned | Not reported | [1137187] |
| Debian | unbound | source | trixie | 1.22.0-2+deb13u3 | not yet assigned | Not reported | [1137187] |
| Debian | unbound | source | bookworm | (unfixed) | not yet assigned | Not reported | [1137187] |
| Cpe | unbound | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | libunbound-dev | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | libunbound8 | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | python3-unbound | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | unbound-anchor | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | unbound-host | cpe | Not reported | 1.19.2-1ubuntu3.8 | Not reported | Not reported | Not reported |
| Cpe | unbound | cpe | Not reported | 1.25.1 | Not reported | Not reported | Not reported |
| Cpe | unbound | cpe | Not reported | 1.25.1 | Not reported | NVD-CVE-2026-42959 | Not reported |
| Alpine | unbound | apk | 3.22 | 1.25.2-r0 | Not reported | ALPINE-CVE-2026-42959 | Not reported |
| Alpine | unbound | apk | 3.23 | 1.25.2-r0 | Not reported | ALPINE-CVE-2026-42959 | Not reported |
| Alpine | unbound | apk | 3.24 | 1.25.1-r0 | Not reported | ALPINE-CVE-2026-42959 | Not reported |
| Ubuntu | unbound | deb | pro | 1.9.4-2ubuntu1.11+esm1 | Not reported | UBUNTU-CVE-2026-42959 | Not reported |
| Ubuntu | unbound | deb | 22.04 | 1.13.1-1ubuntu5.15 | Not reported | UBUNTU-CVE-2026-42959 | Not reported |
| Ubuntu | unbound | deb | 24.04 | 1.19.2-1ubuntu3.8 | Not reported | UBUNTU-CVE-2026-42959 | Not reported |
| Ubuntu | unbound | deb | 25.10 | 1.22.0-2ubuntu2.3 | Not reported | UBUNTU-CVE-2026-42959 | Not reported |
| Ubuntu | unbound | deb | 26.04 | 1.24.2-1ubuntu2.1 | Not reported | UBUNTU-CVE-2026-42959 | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libunbound8]Affected
Source package: [unbound]
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- [libunbound-dev]Affected
Source package: [unbound]
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- [python3-unbound]Affected
Source package: [unbound]
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- [unbound]Affected
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- [unbound-anchor]Affected
Source package: [unbound]
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- [unbound-host]Affected
Source package: [unbound]
Details (4)
1.17.1-2+deb12u4· amd64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u4· arm64 · bookwormAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· amd64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
1.17.1-2+deb12u3· arm64 · bookworm-securityAffected
nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[Debian 13 (Trixie)]
- [libunbound8]Fixed
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
- [libunbound-dev]Fixed
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
- [python3-unbound]Fixed
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
- [unbound]Fixed
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
- [unbound-anchor]Fixed
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
- [unbound-host]Fixed
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.22.0-2+deb13u3nvd · unbound · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/suse-su-2026_21874-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-42959]
- [https://osv.dev/vulnerability/ALPINE-CVE-2026-42959]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-42959]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-42959]
- [https://security-tracker.debian.org/tracker/CVE-2026-42959]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42959.json]
- [https://ubuntu.com/security/notices/USN-8282-1]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-2455.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]