CVE-2026-86409
Description
A flaw was found in curl. When an application attempts to disable Amazon Web Services Signature Version 4 (AWS SigV4) authentication on a reused connection handle, curl fails to clear the setting as expected. If the application subsequently directs a request to an untrusted or attacker-controlled server using the same handle, curl unintentionally transmits the signed authorization header. This flaw allows a remote attacker to obtain access key identifiers and request signatures, leading to information disclosure.
Statement
This vulnerability is rated as Low impact because it does not affect the standard curl command-line utility and requires a highly specific programmatic workflow in applications using libcurl. Triggering the flaw requires an application to reuse transfer handles across differing trust boundaries, attempt to clear AWS SigV4 authentication by resetting the option to null, and direct subsequent requests to untrusted targets. Furthermore, the resulting exposure is restricted to the access key identifier and a request-bound signature, leaving the secret key uncompromised.
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 | 5.3 | N/A | 8.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | None | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Acknowledgements
Red Hat would like to thank Stanislav Fort (Aisle Research) for reporting this issue.
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