CVE-2025-9086: Haxx Curl out-of-bounds read (CVSS 7.5)

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 only a slash as path (`path="/"`). Since this site is not secure, the cookie *should* 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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Haxx Curl≥ 8.13.0 < 8.16.0

Debian Linux11.0

Remediation

Fixed in

Haxx Curl≥ 8.16.0

Patch & vendor advisories

References

https://cert-portal.siemens.com/productcert/html/ssa-089022.html
https://cert-portal.siemens.com/productcert/html/ssa-253495.html
https://curl.se/docs/CVE-2025-9086.htmlPatchVendor Advisory
https://curl.se/docs/CVE-2025-9086.jsonVendor Advisory
https://hackerone.com/reports/3294999ExploitIssue TrackingThird Party Advisory
https://lists.debian.org/debian-lts-announce/2026/01/msg00002.htmlMailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2025/09/10/1Mailing ListPatchThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2025-9086 being actively exploited?

CVE-2025-9086 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.40%.

How severe is CVE-2025-9086?

CVE-2025-9086 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 1.40% probability of exploitation.

Which products are affected by CVE-2025-9086?

Affected products include Haxx Curl, Debian Linux.

How do I fix CVE-2025-9086?

Upgrade affected software to a fixed version, for example Haxx Curl 8.16.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-9086 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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