CVE-2025-9086

Summary

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.

Affected Software

Weaknesses

• CWE-125: Out-of-bounds Read

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

CVE Program Container

Additional References

• http://www.openwall.com/lists/oss-security/2025/09/10/1
• https://lists.debian.org/debian-lts-announce/2026/01/msg00002.html

Additional References

• https://cert-portal.siemens.com/productcert/html/ssa-089022.html
• https://cert-portal.siemens.com/productcert/html/ssa-253495.html

References

• https://curl.se/docs/CVE-2025-9086.json
• https://curl.se/docs/CVE-2025-9086.html
• https://hackerone.com/reports/3294999

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