High 7.5Published Mar 3, 2022

CVE-2021-3737A flaw was found in python.

Updated under an hour ago (Oct 26, 2026, 10:23 PM ET)

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It affects Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP and 19 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP

Exploited in the last 30 days

A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time. The highest threat from this vulnerability is to system availability.

CVSS: 7.5 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-835
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: redhat
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 14, 2026

Affected products

Affected products

Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.0 before V3.1.5	CISA ADP
python python python:python	from 3.6.0 before 3.6.14; from 3.7.0 before 3.7.11; from 3.8.0 before 3.8.11; from 3.9.0 before 3.9.6	NVD
redhat codeready_linux_builder redhat:codeready_linux_builder	8.0	NVD
redhat codeready_linux_builder_for_ibm_z_systems redhat:codeready_linux_builder_for_ibm_z_systems	8.0	NVD
redhat codeready_linux_builder_for_power_little_endian redhat:codeready_linux_builder_for_power_little_endian	8.0	NVD
redhat enterprise_linux redhat:enterprise_linux	6.0; 7.0; 8.0	NVD
redhat enterprise_linux_for_ibm_z_systems redhat:enterprise_linux_for_ibm_z_systems	8.0	NVD
redhat enterprise_linux_for_power_little_endian redhat:enterprise_linux_for_power_little_endian	8.0	NVD
1–10 of 20

References

References

https://bugs.python.org/issue44022	exploit, issue-tracking, vendor-advisory
https://github.com/python/cpython/pull/25916	patch, third-party-advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1995162	issue-tracking, patch, third-party-advisory
https://github.com/python/cpython/pull/26503	patch, third-party-advisory
https://ubuntu.com/security/CVE-2021-3737	patch, third-party-advisory
https://www.oracle.com/security-alerts/cpujul2022.html	patch, third-party-advisory
https://python-security.readthedocs.io/vuln/urllib-100-continue-loop.html	patch, third-party-advisory
https://security.netapp.com/advisory/ntap-20220407-0009/	third-party-advisory
https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html	mailing-list
https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html	mailing-list
1–10 of 13

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.