CVE-2026-82209 domain-scoped PSL domain cookie
Attackers can bypass cookie domain restrictions in libcurl to leak cookies to sibling subdomains when libpsl is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82209?
CVE-2026-82209 is a high-severity vulnerability in Haxx Curl, published on 6 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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`).
Weakness: CWE-201
Which versions are affected by CVE-2026-82209?
It affects 1 product.
Products include Haxx Curl.
How do I fix CVE-2026-82209?
Apply the vendor's patch.
Is CVE-2026-82209 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82209 exists.
Other vulnerabilities in Haxx Curl
Sources
Also known as ALPINE-CVE-2026-82209, AZL-99767, AZL-99783, AZL-99804, AZL-99825, AZL-99852 and 15 more.