CVE-2026-6019

Summary

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.

Affected Software

Weaknesses

• CWE-150: CWE-150 Improper neutralization of escape, meta, or control sequences

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

References

• https://github.com/python/cpython/pull/148848
• https://github.com/python/cpython/issues/90309
• https://mail.python.org/archives/list/security-announce@python.org/thread/IVNWGV2BBNC3RHQAFS22UP4DY56SAXX3/
• https://github.com/python/cpython/commit/76b3923d688c0efc580658476c5f525ec8735104
• https://github.com/python/cpython/commit/3c59b8b53fc75c7f9578d16fb8201ceb43e8f76c
• https://github.com/python/cpython/commit/f795e042043dfe26c42e1971d4502c1cdc4c65b8

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