CVE-2026-6019

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.

References

• https://github.com/python/cpython/commit/76b3923d688c0efc580658476c5f525ec8735104
• https://github.com/python/cpython/issues/90309
• https://github.com/python/cpython/pull/148848
• https://mail.python.org/archives/list/security-announce@python.org/thread/IVNWGV2BBNC3RHQAFS22UP4DY56SAXX3/