# CVE-2026-1502: HTTP client proxy tunnel headers not validated for CR/LF

Status: published. Published: 2026-04-10. Updated: 2026-11-13.

CR/LF bytes were not rejected by HTTP client proxy tunnel headers or host.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/pull/146212
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/05ed7ce7ae9e17c23a04085b2539fe6d6d3cef69
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/b1cf9016335cb637c5a425032e8274a224f4b2ed
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/9e071c9b28c17f347f81b388a003d4eeb3c7a8dd
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/c00c386faa579ad71196d33408644478488e43ec
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/56b7100b04e44ea27989242b176beb8f016b2c53
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: PSF) — https://github.com/python/cpython/commit/58703ec1bdd1eb075e8b01a0c427683ce594dd3e

## Affected products and versions

- Python Software Foundation / CPython (http.client): ≥ 0; < 3.10.21 (affected, python); ≥ 3.11.0; < 3.11.16 (affected, python); ≥ 3.12.0; < 3.12.14 (affected, python); ≥ 3.13.0; < 3.13.14 (affected, python); ≥ 3.14.0a1; < 3.14.5rc1 (affected, python); ≥ 3.15.0a1; < 3.15.0b1 (affected, python). Source: CNA: PSF
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 4.0: 5.7 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N; source: CNA: PSF

- CVSS 4.0: 5.7 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: cna@python.org

- CISA KEV: No listing in collected sources

- EPSS: 0.53% as of 2026-11-13; percentile 45.67%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-93

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/python/cpython/pull/146212 (CNA: PSF; patch)

- https://github.com/python/cpython/issues/146211 (CNA: PSF; issue-tracking)

- https://mail.python.org/archives/list/security-announce@python.org/thread/2IVPAEQWUJBCTQZEJEVTYCIKSMQPGRZ3/ (CNA: PSF; vendor-advisory)

- https://github.com/python/cpython/commit/05ed7ce7ae9e17c23a04085b2539fe6d6d3cef69 (CNA: PSF; patch)

- https://github.com/python/cpython/commit/b1cf9016335cb637c5a425032e8274a224f4b2ed (CNA: PSF; patch)

- https://github.com/python/cpython/commit/9e071c9b28c17f347f81b388a003d4eeb3c7a8dd (CNA: PSF; patch)

- https://github.com/python/cpython/commit/c00c386faa579ad71196d33408644478488e43ec (CNA: PSF; patch)

- https://github.com/python/cpython/commit/56b7100b04e44ea27989242b176beb8f016b2c53 (CNA: PSF; patch)

- https://github.com/python/cpython/commit/58703ec1bdd1eb075e8b01a0c427683ce594dd3e (CNA: PSF; patch)

- http://www.openwall.com/lists/oss-security/2026/04/11/4 (ADP: CVE)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

- https://github.com/python/cpython/commit/05ed7ce7ae9e17c23a04085b2539fe6d6d3cef69 (cna@python.org)

- https://github.com/python/cpython/commit/56b7100b04e44ea27989242b176beb8f016b2c53 (cna@python.org)

- https://github.com/python/cpython/commit/58703ec1bdd1eb075e8b01a0c427683ce594dd3e (cna@python.org)

- https://github.com/python/cpython/commit/9e071c9b28c17f347f81b388a003d4eeb3c7a8dd (cna@python.org)

- https://github.com/python/cpython/commit/b1cf9016335cb637c5a425032e8274a224f4b2ed (cna@python.org)

- https://github.com/python/cpython/commit/c00c386faa579ad71196d33408644478488e43ec (cna@python.org)

- https://github.com/python/cpython/issues/146211 (cna@python.org)

- https://github.com/python/cpython/pull/146212 (cna@python.org)

- https://mail.python.org/archives/list/security-announce@python.org/thread/2IVPAEQWUJBCTQZEJEVTYCIKSMQPGRZ3/ (cna@python.org)

- http://www.openwall.com/lists/oss-security/2026/04/11/4 (af854a3a-2127-422b-91ae-364da2661108)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (0b142b55-0307-4c5a-b3c9-f314f3fb7c5e)

## Provenance

- CNA: PSF: https://www.cve.org/CVERecord?id=CVE-2026-1502; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1502; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-1502; retrieved 2026-11-13; source updated Not reported

Revision: 314fa9509d23081d4c6dd9f6d96bdabaa7052a6fbbfd3e900eb4638e0762df01

Canonical: https://y2.dev/cve/CVE-2026-1502

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.