Header injection via CRLF in data URL mediatype
Published Jan 20, 2026 · Updated Jan 20, 2026
CRLF injection in urllib.request.DataHandler in affected Python Software Foundation CPython releases allows attackers to inject headers through crafted data URLs. The data_open method split the mediatype from the payload and passed it to an email header parser without rejecting C0 controls or DEL, so embedded newlines became additional header fields. Exploitation requires an application to pass attacker-controlled data URLs into urllib.request; injected fields can alter downstream header handling.
Summary
What happened
CRLF injection in urllib.request.DataHandler in affected Python Software Foundation CPython releases allows attackers to inject headers through crafted data URLs. The data_open method split the mediatype from the payload and passed it to an email header parser without rejecting C0 controls or DEL, so embedded newlines became additional header fields. Exploitation requires an application to pass attacker-controlled data URLs into urllib.request; injected fields can alter downstream header handling.
The record
- CVE
- CVE-2025-15282
- Published
- Jan 20, 2026
- Updated
- Jan 20, 2026
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-93
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 20, 2026CVE publishedPublication date reported by the CVE source.
- Jan 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <3.15.0
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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