What’s Vulnerable › Vulnerabilities

CVE-2025-15282: Header injection via newlines in data URL mediatype

• Severity: medium (CVSS 6.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-01-20 · updated 2026-06-17
• Weakness: CWE-93

Description

User-controlled data URLs parsed by urllib.request.DataHandler allow injecting headers through newlines in the data URL mediatype.

Affected products

• Python: before 3.10.20; from 3.11.0 before 3.11.15; from 3.12.0 before 3.12.13; from 3.13.0 before 3.13.12; from 3.14.0 before 3.14.3; from 3.15.0a1 before 3.15.0a6 — fixed in 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3, 3.15.0a6

How to fix

Upgrade to a fixed version: Python 3.10.20, 3.11.15, 3.12.13, 3.13.12. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/05356b1cc153108aaf27f3b72ce438af4aa218c0
• https://github.com/python/cpython/commit/34d76b00dabde81a793bd06dd8ecb057838c4b38
• https://github.com/python/cpython/commit/3f396ca9d7bbe2a50ea6b8c9b27c0082884d9f80
• https://github.com/python/cpython/commit/4ed11d3cd288e6b90196a15c5a825a45d318fe47
• https://github.com/python/cpython/commit/a35ca3be5842505dab74dc0b90b89cde0405017a
• https://github.com/python/cpython/commit/f25509e78e8be6ea73c811ac2b8c928c28841b9f
• https://github.com/python/cpython/issues/143925
• https://github.com/python/cpython/pull/143926
• https://mail.python.org/archives/list/security-announce@python.org/thread/X66HL7SISGJT33J53OHXMZT4DFLMHVKF/

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