CVE-2026-86414
Description
A flaw was found in curl. A malicious or compromised HTTP proxy server can trick curl into sending authentication credentials intended for the target destination server directly to the proxy itself. When establishing a connection tunnel, if the proxy replies with an HTTP 401 Unauthorized status code instead of a proxy authentication challenge, curl mishandles the response and transmits the origin server's credentials. This issue leads to information disclosure, allowing an untrusted proxy to intercept sensitive passwords and authentication tokens.
Statement
This vulnerability is rated as having a Low security impact because exploitation relies on routing outbound traffic through an untrusted or compromised HTTP proxy server. In standard Red Hat Enterprise Linux environments, proxy infrastructure is centrally managed within trusted network boundaries, significantly minimizing the likelihood of a rogue proxy tampering with tunnel handshakes. Furthermore, target endpoint authentication credentials are only exposed if a client actively transmits authentication data over a proxied tunnel.
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 | 6.5 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| 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 | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Files or Directories; Read Memory; Read Application Data
Sensitive data may be exposed to attackers.
Acknowledgements
Red Hat would like to thank Stanislav Fort (Aisle Research) for reporting this issue.
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