CVE-2025-9086

Technical Description

1. A cookie is set using the `secure` keyword for `https://target`

2. curl is redirected to or otherwise made to speak with `http://target` (same

hostname, but using clear text HTTP) using the same cookie set

3. The same cookie name is set - but with just a slash as path (`path=\"/\",`).

Since this site is not secure, the cookie *should* just be ignored.

4. A bug in the path comparison logic makes curl read outside a heap buffer

boundary

The bug either causes a crash or it potentially makes the comparison come to

the wrong conclusion and lets the clear-text site override the contents of the

secure cookie, contrary to expectations and depending on the memory contents

immediately following the single-byte allocation that holds the path.

The presumed and correct behavior would be to plainly ignore the second set of

the cookie since it was already set as secure on a secure host so overriding

it on an insecure host should not be okay.

Remediation

Check the references section for vendor advisories and patches from haxx. Update curl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References