CVE-2026-6019
BaseCookie.js_output() does not neutralize embedded characters
6.1CVSSMEDIUM
Description
http.cookies.Morsel.js_output() returns an inline <script> snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence </script> inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value.
CVSS Vector Breakdown
Exploitability
AV:NAttack VectorNetwork
AC:LAttack ComplexityLow
PR:NPrivileges RequiredNone
UI:RUser InteractionRequired
Scope
S:CScopeChanged
Impact
C:LConfidentialityLow
I:LIntegrityLow
A:NAvailabilityNone
Weaknesses
Affected Products
Exploitability
Official Patch Available
References
https://github.com/python/cpython/pull/148848
github.com
https://github.com/python/cpython/issues/90309
github.com
https://mail.python.org/archives/list/security-announce@python.org/thread/IVNWGV2BBNC3RHQAFS22UP4DY56SAXX3/
mail.python.org
and 3 more references View all →
Timeline
Published
Apr 22, 2026
Last Updated
May 28, 2026
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