CVE-2026-82717
Description
A flaw was found in Unbound. A remote attacker could exploit a vulnerability during CNAME (Canonical Name) synthesis when processing an upstream DNS response. This flaw, involving improper handling of buffer positions and compression pointers, can progressively corrupt heap memory. This memory corruption can lead to a denial of service (DoS) due to a crash, and under specific conditions, it may enable remote code execution.
Statement
This is an Important vulnerability in Unbound that could lead to remote code execution due to heap memory corruption during CNAME synthesis. As Unbound is a critical DNS resolver component in Red Hat environments, successful exploitation could severely impact service availability and integrity. The complexity of exploiting heap memory corruption may limit immediate widespread attacks.
Mitigation
To mitigate this restrict Unbound to trusted clients and limit which upstream name servers it can query. If Unbound is unused, disable or remove the service. Apply process/cgroup limits to contain crash impact.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | High | N/A | N/A |
| Integrity Impact | High | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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