CVE-2025-8677
Description
A vulnerability was found in BIND 9 resolvers, where processing malformed DNSKEY records from a specially crafted zone can lead to resource exhaustion, primarily causing excessive CPU utilization. This issue enables a remote, unauthenticated attacker to degrade resolver performance and potentially cause a denial of service (DoS) for legitimate DNS clients.
Statement
This vulnerability is considered Important because it allows a remote, unauthenticated attacker to cause significant CPU exhaustion on vulnerable BIND resolvers by serving zones containing malformed DNSKEY records. The flaw triggers excessive computational effort during DNSKEY validation, leading to degraded performance and potential denial of service for legitimate clients. However, the issue affects availability only—it does not enable code execution, data exposure, or privilege escalation—so it is not classified as critical. Furthermore, authoritative servers are not impacted, limiting the scope of exposure to recursive resolvers. While the attack is easy to launch and can disrupt DNS operations, its effect ceases once the malicious traffic stops, making prompt patching and recursive access control effective mitigations.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
To reduce risk, restrict recursive queries to trusted or internal networks only, and apply rate limiting or firewall rules to prevent excessive or repetitive requests. Enabling DNSSEC validation helps reject forged records, while isolating recursive resolvers from authoritative servers limits the impact of potential cache poisoning. Active monitoring of CPU usage, query volume, and cache anomalies can provide early warning of abuse or attacks.
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 | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
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