CVE-2026-87862
Description
A flaw was found in curl. When importing HTTP Strict Transport Security (HSTS) cache records, loading a parent domain entry configured to include subdomains before a longer-lived subdomain entry silently drops the subdomain policy. Consequently, once the parent policy expires, curl fails to upgrade subsequent connections for the subdomain to HTTPS and transmits unencrypted requests, allowing a network attacker to intercept sensitive data.
Statement
Red Hat has rated this vulnerability as Low impact because exploitation depends on non-default HSTS cache usage and requires an attacker to be positioned on-path to capture unencrypted traffic once the parent rule lapses. In typical Red Hat environments, applications and administrative scripts invoke curl using explicit HTTPS URLs rather than relying on opportunistic HSTS upgrades from a shared cache file. Additionally, curl does not enable HSTS cache loading by default, substantially limiting exposure across standard deployments.
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 | 3.7 | N/A | 8.1 |
| 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 | Low | 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:N/S:U/C:L/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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