CVE-2026-101283
Description
A flaw was found in iperf3. When configured with RSA authentication, the application fails to properly validate the length of incoming encrypted authentication messages before copying them into a fixed-size memory buffer. An unauthenticated remote attacker can exploit this vulnerability by sending an oversized authentication token, triggering a heap-based buffer overflow. This vulnerability could allow an attacker to execute arbitrary code or crash the application, resulting in a Denial of Service (DoS).
Statement
A heap buffer overflow was found in iperf3's decrypt_rsa_message() when RSA authentication is enabled. The function reads attacker-controlled ciphertext into a fixed-size RSA buffer using BIO_read() with a client-supplied length, and the existing length guard only warns rather than rejecting oversized input. An unauthenticated remote client can send an oversized authtoken and corrupt heap memory, crashing the iperf3 server and potentially achieving code execution in the iperf3 process. Exploitation requires a non-default server configuration with both --rsa-private-key-path and --authorized-users-path. The issue affects iperf3 3.20 and 3.21 (fixed in 3.22). Red Hat rates this Important (CVSSv3.1 8.1, AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).
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. Upstream has fixed this issue in iperf3 3.22; upgrading to a version that contains the fix is the recommended 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).
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
Red Hat CVSS v3 Score Explanation
AC:H because exploitation requires the server to be started with RSA authentication (--rsa-private-key-path and --authorized-users-path). Default iperf3 servers are not exposed. C/I/A:H reflect heap memory corruption from an attacker-controlled BIO_read length into a fixed-size RSA buffer; practical outcome includes process crash and potential code execution in the iperf3 process.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Modify Memory
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
