CVE-2026-42955
Description
A "ghost domain names" flaw in Unbound allows a remote attacker controlling a domain to manipulate cached DNS records. By extending the lifetime of outdated DNS information, an attacker can cause clients to receive stale or misleading DNS responses.
Statement
This Low impact DNS cache integrity issue in Unbound allows an attacker to extend the window for serving outdated DNS information. Exploitation requires an adversary to control a ghost zone and query a vulnerable Unbound instance. The risk is elevated if the non-default harden-referral-path: yes configuration is enabled, as it removes the need for a client query.
Mitigation
To mitigate this issue, ensure harden-referral-path is set to no (the default) to prevent Unbound from implicitly triggering the vulnerable cache overwrites.
Additionally, restrict recursive DNS access strictly to trusted clients to prevent external attackers from manually triggering the flaw.
Restart the Unbound service to apply these configuration changes.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | N/A | 3.7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Modify Application Data; Other
Integrity checks usually use a secret key that helps authenticate the data origin. Skipping integrity checking generally opens up the possibility that new data from an invalid source can be injected.
Integrity,Other
Technical Impact: Other
Data that is parsed and used may be corrupted.
Non-Repudiation,Other
Technical Impact: Hide Activities; Other
Without a checksum check, it is impossible to determine if any changes have been made to the data after it was sent.
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