CVE-2026-82209
Received Received - Intake

Cookie Domain Spoofing in libcurl with Public Suffix List

Publication date: 2026-09-06

Last updated on: 2026-09-06

Assigner: curl

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`).

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Meta Information

Published
2026-09-06
Last Modified
2026-09-06
Generated
2026-09-08
AI Q&A
2026-09-06
EPSS Evaluated
N/A
NVD
CVE-2026-82209
EUVD
EUVD-2026-72153

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
curl curl From 7.46.0 (inc) to 8.21.0 (inc)
curl curl 8.22.0
curl curl From 7.46.0 (inc) to 8.22.0 (exc)
curl libcurl *

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability occurs in libcurl when libpsl support is enabled. When processing a Set-Cookie header with a Domain attribute matching an origin host that is a public suffix (like co.uk), libcurl incorrectly assigns a wildcard domain scope (.co.uk) instead of treating it as a strict host-only cookie. This causes the cookie to be sent to arbitrary sibling subdomains under the same public suffix, such as attacker.co.uk.

Detection Guidance

Check curl version with 'curl --version' to see if it falls within the vulnerable range (7.46.0 to 8.21.0). If using libpsl, inspect cookie handling behavior by monitoring Set-Cookie headers with Domain attributes matching public suffixes like 'co.uk'.

Impact Analysis

If you use a vulnerable version of curl (7.46.0 to 8.21.0) with libpsl enabled, cookies set by a public suffix domain (e.g., co.uk) could be sent to unintended sibling subdomains (e.g., attacker.co.uk). This may expose sensitive data in requests to those subdomains, leading to information leakage.

Compliance Impact

This vulnerability could lead to unauthorized data exposure, potentially violating privacy regulations like GDPR or HIPAA by sending sensitive cookies to untrusted domains. Organizations must ensure they use patched versions of curl to maintain compliance.

Mitigation Strategies

Upgrade curl to version 8.22.0 or later. Alternatively, disable libpsl support if upgrading is not possible, or avoid using cookies in applications until patched.

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