CVE-2026-86410
Description
A flaw was found in the curl command-line tool. When configured to follow redirects to Secure File Transfer Protocol (SFTP) or Secure Copy Protocol (SCP) destinations, curl fails to apply user-specified Secure Shell (SSH) host verification settings. A malicious server can exploit this flaw by redirecting requests to an untrusted server, causing the connection to proceed without validating the remote host's identity. This failure can enable an attacker to intercept communications, leading to sensitive information disclosure.
Statement
Red Hat has evaluated this vulnerability as having a Low severity impact because exploitation requires an uncommon combination of non-default command-line flags and does not affect applications utilizing libcurl. Under standard configurations, curl restricts redirect targets and prevents following redirects to SSH protocols by default. A risk of omitted SSH host verification only arises when a user explicitly directs the standalone curl command-line binary to follow redirects and overrides protocol restrictions to allow SFTP or SCP.
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 | 6.8 | 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 | Required | 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 | None | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity
The data read from the system vouched for by the certificate may not be from the expected system.
Authentication,Other
Technical Impact: Other
Trust afforded to the system in question - based on the malicious certificate - may allow for spoofing or redirection attacks.
Access Control,Other
Technical Impact: Gain Privileges or Assume Identity; Other
If the certificate's host-specific data is not properly checked - such as the Common Name (CN) in the Subject or the Subject Alternative Name (SAN) extension of an X.509 certificate - it may be possible for a redirection or spoofing attack to allow a malicious host with a valid certificate to provide data, impersonating a trusted host.
Acknowledgements
Red Hat would like to thank Stanislav Fort (Aisle Research) for reporting this issue.
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