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Vulnerability record · CVE-2020-26137 · published 30 September 2020

CVE-2020-26137: Python urllib3 injection vulnerability

Python · Urllib3

urllib3 before 1.25.9 allows CRLF injection if the attacker controls the HTTP request method, as demonstrated by inserting CR and LF control characters in the first argument of putrequest(). NOTE: this is similar to CVE-2020-26116.

6.5 CVSS 3.1 Medium EPSS 2.3% · top 17.6% CWE-74 · Injection
6.5CVSS 3.1 base score, v2 6.4
2.3%EPSS exploitation probability, 30 days
NoNot in CISA KEV
5Affected product versions listed by NVD
16References
17 Jun 2026Last modified by NVD

Description

urllib3 before 1.25.9 allows CRLF injection if the attacker controls the HTTP request method, as demonstrated by inserting CR and LF control characters in the first argument of putrequest(). NOTE: this is similar to CVE-2020-26116.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

5 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.python.org/issue39603 Issue TrackingVendor Advisory
https://github.com/urllib3/urllib3/commit/1dd69c5c5982fae7c87a620d487c2ebf7a6b436b PatchThird Party Advisory
https://github.com/urllib3/urllib3/pull/1800 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/06/msg00015.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/10/msg00012.html
https://usn.ubuntu.com/4570-1/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory
https://bugs.python.org/issue39603 Issue TrackingVendor Advisory
https://github.com/urllib3/urllib3/commit/1dd69c5c5982fae7c87a620d487c2ebf7a6b436b PatchThird Party Advisory
https://github.com/urllib3/urllib3/pull/1800 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/06/msg00015.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/10/msg00012.html
https://usn.ubuntu.com/4570-1/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-26137), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.