CVE-2026-62309
Description
A flaw was found in CoreDNS. A remote attacker can send a specially crafted 28-byte UDP datagram to a CoreDNS server with the proxyproto plugin enabled. This malformed datagram can cause the CoreDNS process to crash, leading to a denial of service (DoS). The vulnerability arises from improper handling of a PROXY v2 header with a non-UDP transport type, which results in a nil pointer dereference.
Statement
This vulnerability is rated as Important because a remote unauthenticated attacker can trigger a denial of service in CoreDNS by sending a specially crafted UDP datagram. This occurs when the proxyproto plugin is enabled, leading to a process crash. Red Hat products utilizing CoreDNS with this plugin enabled are susceptible to service disruption.
Mitigation
To mitigate this vulnerability, disable the `proxyproto` plugin in your CoreDNS configuration if it is not strictly required. If the `proxyproto` plugin is essential for your deployment, restrict network access to the CoreDNS service to only trusted sources. This can be achieved by configuring firewall rules to limit UDP traffic on the CoreDNS port. Any changes to the CoreDNS configuration will require a restart or reload of the CoreDNS service to take effect, which may temporarily disrupt DNS resolution.
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
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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