Proxy CONNECT request injection via unsanitized CRLF
Published Apr 10, 2026 · Updated Apr 10, 2026
HTTP header injection in CPython http.client allows remote authenticated users to modify outbound proxy CONNECT requests. The _tunnel method serialized set_tunnel host and header values directly into the CONNECT request without rejecting CR or LF bytes. Exploitation requires an application to pass attacker-controlled tunnel data under a high-privilege context; injected line breaks can add arbitrary proxy request fields.
Summary
What happened
HTTP header injection in CPython http.client allows remote authenticated users to modify outbound proxy CONNECT requests. The _tunnel method serialized set_tunnel host and header values directly into the CONNECT request without rejecting CR or LF bytes. Exploitation requires an application to pass attacker-controlled tunnel data under a high-privilege context; injected line breaks can add arbitrary proxy request fields.
The record
- CVE
- CVE-2026-1502
- Published
- Apr 10, 2026
- Updated
- Apr 10, 2026
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-93
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Apr 10, 2026CVE publishedPublication date reported by the CVE source.
- Apr 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
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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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