Upstream information
Description
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.SUSE information
Overall state of this security issue: Pending
This issue is currently rated as having moderate severity.
| CVSS detail | CNA (NLnet Labs) | SUSE |
|---|---|---|
| Base Score | 5.3 | 5.9 |
| Vector | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N |
| Attack Vector | Adjacent Network | Network |
| Attack Complexity | High | High |
| Privileges Required | None | None |
| User Interaction | None | None |
| Scope | Unchanged | Unchanged |
| Confidentiality Impact | None | None |
| Integrity Impact | High | High |
| Availability Impact | None | None |
| CVSSv3 Version | 3.1 | 3.1 |
| CVSS detail | SUSE |
|---|---|
| Base Score | 8.2 |
| Vector | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |
| Attack Vector | Network |
| Attack Complexity | Low |
| Attack Requirements | Present |
| Privileges Required | None |
| User Interaction | None |
| Vulnerable System Confidentiality Impact | None |
| Vulnerable System Integrity Impact | High |
| Vulnerable System Availability Impact | None |
| Subsequent System Confidentiality Impact | None |
| Subsequent System Integrity Impact | None |
| Subsequent System Availability Impact | None |
| CVSSv4 Version | 4.0 |
List of released packages
| Product(s) | Fixed package version(s) | References |
|---|---|---|
| openSUSE Tumbleweed |
| Patchnames: openSUSE-Tumbleweed-2026-12257 |
Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise Desktop 15 SP7 | unbound | Affected |
| SUSE Linux Enterprise Micro 5.5 | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | unbound | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP7 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP7 | unbound | Affected |
| SUSE Linux Enterprise Server 16.0 | unbound | In progress |
| SUSE Linux Enterprise Server 16.1 | unbound | In progress |
| SUSE Linux Enterprise Server 16.2 | unbound | Affected |
| SUSE Linux Enterprise Server for NVIDIA 16.1 | unbound | In progress |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | unbound | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | unbound | In progress |
| SUSE Linux Enterprise Server for SAP applications 16.1 | unbound | In progress |
| SUSE Linux Enterprise Server for SAP applications 16.2 | unbound | Affected |
| SUSE Linux Micro 6.0 | unbound | In progress |
| SUSE Linux Micro 6.1 | unbound | In progress |
| SUSE Linux Micro 6.2 | unbound | In progress |
| openSUSE Leap 16.0 | unbound | Affected |
| openSUSE Leap 16.1 | unbound | Affected |
| Products under Long Term Service Pack support and receiving important and critical security fixes. | ||
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP6 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP6 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | unbound | Affected |
| Products past their end of life and not receiving proactive updates anymore. | ||
| SUSE CaaS Platform 4.0 | unbound | Affected |
| SUSE Enterprise Storage 6 | unbound | Affected |
| SUSE Enterprise Storage 7 | unbound | Affected |
| SUSE Enterprise Storage 7.1 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP1 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | unbound | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP1 | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | unbound | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | unbound | Affected |
| SUSE Linux Enterprise Real Time 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise Real Time 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise Real Time 15 SP4 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP1 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP1-BCL | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP3 | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | unbound | Affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP1 | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | unbound | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | unbound | Affected |
| SUSE Manager Proxy 4.0 | unbound | Affected |
| SUSE Manager Proxy 4.1 | unbound | Affected |
| SUSE Manager Proxy 4.2 | unbound | Affected |
| SUSE Manager Proxy 4.3 | unbound | Affected |
| SUSE Manager Proxy LTS 4.3 | unbound | Affected |
| SUSE Manager Retail Branch Server 4.0 | unbound | Affected |
| SUSE Manager Retail Branch Server 4.1 | unbound | Affected |
| SUSE Manager Retail Branch Server 4.2 | unbound | Affected |
| SUSE Manager Retail Branch Server 4.3 | unbound | Affected |
| SUSE Manager Retail Branch Server LTS 4.3 | unbound | Affected |
| SUSE Manager Server 4.0 | unbound | Affected |
| SUSE Manager Server 4.1 | unbound | Affected |
| SUSE Manager Server 4.2 | unbound | Affected |
| SUSE Manager Server 4.3 | unbound | Affected |
| SUSE Manager Server LTS 4.3 | unbound | Affected |
| openSUSE Leap 15.3 | unbound | Affected |
| openSUSE Leap 15.4 | unbound | Affected |
| openSUSE Leap 15.5 | unbound | Affected |
| openSUSE Leap 15.6 | unbound | Affected |
SUSE Timeline for this CVE
CVE page created: Fri Oct 23 12:55:18 2026CVE page last modified: Mon Oct 26 17:55:54 2026