CVE-2026-71310
Description
A flaw was found in rclone. A remote attacker, by controlling a malicious or compromised proxy server or acting as an on-path attacker for a plaintext HTTP proxy connection, could send oversized HTTP CONNECT response headers. The rclone application's HTTP CONNECT helper processes these responses using an unrestricted buffered reader, leading to unbounded memory growth. This can cause the rclone process to exhaust its memory and terminate, resulting in a Denial of Service (DoS). This vulnerability affects FTP and SFTP proxy connections, with SFTP being vulnerable even before SSH server authentication.
Statement
This Moderate impact denial of service flaw in rclone arises from unbounded memory growth when processing oversized HTTP CONNECT response headers via FTP or SFTP proxy connections. Exploitation requires a malicious or compromised proxy server, or an active on-path attacker, which limits the attack vector and increases attack complexity.
Mitigation
Avoid routing rclone FTP or SFTP connections through untrusted HTTP proxies. If a proxy is required, ensure it
is a trusted, internally controlled endpoint. No mitigation is needed for deployments that do not use HTTP proxies for rclone connections.
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 | 5.9 | N/A | 5.9 |
| 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 | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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