Description
When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a `Set-Cookie` header where the `Domain` attribute explicitly matches an origin host that is itself a public suffix (e.g., `Domain=co.uk` set by `co.uk`). Instead of coercing it into a strict host-only cookie, libcurl saves the cookie with wildcard domain scope (`.co.uk`). Consequently, the cookie is inappropriately included in subsequent outbound requests or HTTP redirects to arbitrary sibling subdomains under the same public suffix (e.g., `attacker.co.uk`).
Affected products
haxx: curl
References4
- curl.se/docs/CVE-2026-82209.html PatchVendor Advisory
- curl.se/docs/CVE-2026-82209.json Vendor Advisory
- hackerone.com/reports/3972385 ExploitMitigationThird Party Advisory
- hackerone.com/reports/3972385 ExploitMitigationThird Party Advisory
Metrics
- CVSS 3.1
-
8.2
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N - EPSS — exploit probability
- 0% percentile: 31 · as of 3 November 2026
- CWE
- CWE-201
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