CVE-2023-46218

curl: information disclosure by exploiting a mixed case flaw

Published Dec 7, 2023 CVSS 3.1 · 6.5 Medium EPSS 1.7% KEV · Not listed
Description
This flaw allows a malicious HTTP server to set "super cookies" in curl that
are then passed back to more origins than what is otherwise allowed or
possible. This allows a site to set cookies that then would get sent to
different and unrelated sites and domains.

It could do this by exploiting a mixed case flaw in curl's function that
verifies a given cookie domain against the Public Suffix List (PSL). For
example a cookie could be set with `domain=co.UK` when the URL used a lower
case hostname `curl.co.uk`, even though `co.uk` is listed as a PSL domain.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3692-1 curl security update
Debian DSA Debian DSA DSA-5587-1 curl security update
Ubuntu USN Ubuntu USN USN-6535-1 curl vulnerabilities
Ubuntu USN Ubuntu USN USN-6641-1 curl vulnerability
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00318}

epss

{'score': 0.00432}

Type Values Removed Values Added
Weaknesses CWE-178
Type Values Removed Values Added
Description This flaw allows a malicious HTTP server to set "super cookies" in curl that are then passed back to more origins than what is otherwise allowed or possible. This allows a site to set cookies that then would get sent to different and unrelated sites and domains. It could do this by exploiting a mixed case flaw in curl's function that verifies a given cookie domain against the Public Suffix List (PSL). For example a cookie could be set with `domain=co.UK` when the URL used a lower case hostname `curl.co.uk`, even though `co.uk` is listed as a PSL domain. This flaw allows a malicious HTTP server to set "super cookies" in curl that are then passed back to more origins than what is otherwise allowed or possible. This allows a site to set cookies that then would get sent to different and unrelated sites and domains. It could do this by exploiting a mixed case flaw in curl's function that verifies a given cookie domain against the Public Suffix List (PSL). For example a cookie could be set with `domain=co.UK` when the URL used a lower case hostname `curl.co.uk`, even though `co.uk` is listed as a PSL domain.

Sources

Status
PUBLISHED
Assigner
hackerone
Published
Updated
Oct 15, 2026, 12:04 AM
Reserved
Oct 19, 2023, 1:00 AM
Status
Modified
Published
Dec 7, 2023, 1:15 AM
Modified
Jun 17, 2026, 6:30 AM
Severity
Moderate
Public date
Dec 6, 2023, 7:00 AM