CVE catalog
CVE-2026-40691
In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer siz
- Severity
- High · CVSS 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.29% · Oct 27, 2026
In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to 'msg-buffer-size', writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support ('--enable-dnscrypt') and the 'dnscrypt:' clause to be configured and enabled for the listening interfaces.
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 | vulnerable |
| 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 |
| Suse | unbound | linux enterprise micro 5.5 | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise high performance computing 15 sp4-espos | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise high performance computing 15 sp4-ltss | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise high performance computing 15 sp5-espos | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise high performance computing 15 sp5-ltss | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise server 15 sp4-ltss | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise server 15 sp5-ltss | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise server for sap applications 15 sp4 | 1.25.2-150100.10.28.1 | fixed |
| Suse | unbound | linux enterprise server for sap applications 15 sp5 | 1.25.2-150100.10.28.1 | 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 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.11+esm2 | vulnerable |
| Ubuntu | unbound | pro | 1.9.4-2ubuntu1.11+esm3 | 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 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.16 | vulnerable |
| Ubuntu | unbound | 22.04 | 1.13.1-1ubuntu5.17 | 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 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.9 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.10 | vulnerable |
| Ubuntu | unbound | 24.04 | 1.19.2-1ubuntu3.12 | fixed |
| Ubuntu | unbound | 26.10 | 1.24.2-1ubuntu2 | vulnerable |
| Ubuntu | unbound | 26.10 | 1.25.1-1ubuntu1 | vulnerable |
| Ubuntu | unbound | 26.10 | 1.25.1-1ubuntu3 | vulnerable |
| 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 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu2.2 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu2.3 | vulnerable |
| Ubuntu | unbound | 26.04 | 1.24.2-1ubuntu2.4 | fixed |
| Cpe | unbound | Not reported | 1.25.2 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | unbound | source | sid | 1.25.2-1 | not yet assigned | Not reported | Not reported |
| Debian | unbound | source | forky | 1.25.2-1 | not yet assigned | Not reported | Not reported |
| Debian | unbound | source | trixie | 1.26.1-0+deb13u1 | not yet assigned | Not reported | Not reported |
| Debian | unbound | source | bookworm | (unfixed) | not yet assigned | Not reported | Not reported |
| Suse | unbound | rpm | linux enterprise micro 5.5 | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise high performance computing 15 sp4-espos | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise high performance computing 15 sp4-ltss | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise high performance computing 15 sp5-espos | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise high performance computing 15 sp5-ltss | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise server 15 sp4-ltss | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise server 15 sp5-ltss | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise server for sap applications 15 sp4 | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Suse | unbound | rpm | linux enterprise server for sap applications 15 sp5 | 1.25.2-150100.10.28.1 | Not reported | SUSE-SU-2026:3884-1 | Not reported |
| Ubuntu | unbound | deb | pro | 1.9.4-2ubuntu1.11+esm3 | Not reported | UBUNTU-CVE-2026-40691 | Not reported |
| Ubuntu | unbound | deb | 22.04 | 1.13.1-1ubuntu5.17 | Not reported | UBUNTU-CVE-2026-40691 | Not reported |
| Ubuntu | unbound | deb | 24.04 | 1.19.2-1ubuntu3.12 | Not reported | UBUNTU-CVE-2026-40691 | Not reported |
| Ubuntu | unbound | deb | 26.04 | 1.24.2-1ubuntu2.4 | Not reported | UBUNTU-CVE-2026-40691 | Not reported |
| Cpe | unbound | cpe | Not reported | 1.25.2 | Not reported | NVD-CVE-2026-40691 | 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]Affected
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
- [libunbound-dev]Affected
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
- [python3-unbound]Affected
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
- [unbound]Affected
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
- [unbound-anchor]Affected
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
- [unbound-host]Affected
Source package: [unbound]
Details (6)
1.22.0-2+deb13u3· amd64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixieAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· amd64 · trixie-security · Historical versionAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.22.0-2+deb13u3· arm64 · trixie-securityAffected · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.1-0+deb13u1· amd64 · trixie-security · Historical versionFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
1.26.2-0+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.26.1-0+deb13u1nvd · unbound · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_11380-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-40691]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-40691]
- [https://osv.dev/vulnerability/SUSE-SU-2026:3884-1]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-40691]
- [https://security-tracker.debian.org/tracker/CVE-2026-40691]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40691.json]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-3038.json]
- [https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-40691.txt]
[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]