CVE catalog

CVE-2026-109125

unbound: CVE-2026-109125

Severity: Medium · CVSS 5.3CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Published: Oct 21, 2026, 9:17:06 AM UTC
Source: [NVD] · [CVE record]
EPSS: 0.17% · Oct 25, 2026

In NLnet Labs Unbound up to and including version 1.26.1, an observable cache-level side-channel can be exposed with 'unwanted-reply-threshold > 0' configurations (not a default configuration). If a response-like UDP datagram reaches the upstream source port currently used by a recursive query, but its TXID does not match any pending query, Unbound counts the packet as an unwanted reply. When the accumulated count reaches the configured threshold, Unbound clears the worker's RRset cache and message cache. This cache clear action does not destroy the current upstream UDP pending query. Therefore, an external observer can distinguish whether a candidate port matches the current upstream source port by checking whether an existing cached item has been cleared. This is a cache side-channel vulnerability that can be used to probe the upstream source port. Although the attack is not feasible on default configurations and the suggested value (10 million) makes it an ureliable attack on a public resolver, in scenarios where the attacker can keep a concurrent query window alive, the attacker can first filter the source port and then perform birthday-style guessing against the TXID, making cache poisoning a feasible attack path.

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
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`	vulnerable
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`	vulnerable
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`	vulnerable
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`	vulnerable
Opensuse	unbound	tumbleweed	`1.26.2-1.1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	unbound	source	sid	`1.26.2-1`	not yet assigned	Not reported	Not reported
Debian	unbound	source	forky	`1.26.2-1`	not yet assigned	Not reported	Not reported
Debian	unbound	source	trixie	`1.26.2-0+deb13u1`	not yet assigned	Not reported	Not reported
Debian	unbound	source	bookworm	`(unfixed)`	not yet assigned	Not reported	Not reported
Opensuse	unbound	rpm	tumbleweed	`1.26.2-1.1`	Not reported	OPENSUSE-SU-2026:12257-1	Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libunbound8]Affected
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
[libunbound-dev]Affected
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
[python3-unbound]Affected
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
[unbound]Affected
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
[unbound-anchor]Affected
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
[unbound-host]Affected
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · unbound · debian · bookworm; dsa · unbound · debian · 12

[Debian 13 (Trixie)]

[libunbound8]Affected
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
[libunbound-dev]Affected
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
[python3-unbound]Affected
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
[unbound]Affected
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
[unbound-anchor]Affected
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
[unbound-host]Affected
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.2-0+deb13u1
  dsa · unbound · debian · 13

[openSUSE Tumbleweed]

[unbound]Affected
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · x86_64 · tumbleweed
  Affected · Fixed: 1.26.2-1.1
  dsa · unbound · opensuse · tumbleweed
[libunbound8]Unknown
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · x86_64 · tumbleweed
  Unknown · Fixed: 1.26.2-1.1
  Version impact unknown
  dsa · unbound · opensuse · tumbleweed
[python3-unbound]Unknown
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · x86_64 · tumbleweed
  Unknown · Fixed: 1.26.2-1.1
  Version impact unknown
  dsa · unbound · opensuse · tumbleweed
[unbound-anchor]Unknown
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · x86_64 · tumbleweed
  Unknown · Fixed: 1.26.2-1.1
  Version impact unknown
  dsa · unbound · opensuse · tumbleweed
[unbound-devel]Unknown
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · x86_64 · tumbleweed
  Unknown · Fixed: 1.26.2-1.1
  Version impact unknown
  dsa · unbound · opensuse · tumbleweed
[unbound-munin]Unknown
Source package: [unbound]
Details (1)
- 1.26.0-2.1 · noarch · tumbleweed
  Unknown · Fixed: 1.26.2-1.1
  Version impact unknown
  dsa · unbound · opensuse · tumbleweed

Observed: Oct 27, 2026, 4:08:10 AM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database]