# CVE-2020-26116 — Python > As of 2026-11-06, CVE-2020-26116 is a HIGH-severity vulnerability in Python, CVSS v3.1 7.2, EPSS 6.3% (93.6th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2020-26116, most recently “Vulnerability in F5 Products (CVE-2020-26116) - Python http.client CRLF Injection in BIG-IP Next SPK, BIG-IQ, F5OS-A, F5OS-C”. **Last updated:** 2026-10-14 ## What is CVE-2020-26116? http.client in Python 3.x before 3.5.10, 3.6.x before 3.6.12, 3.7.x before 3.7.9, and 3.8.x before 3.8.5 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 HTTPConnection.request. The record classifies CVE-2020-26116 under weakness class [CWE-74](https://intel.threadlinqs.com/cwe/CWE-74). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 14 affected-product entries are recorded, across 7 vendors, listed below. The identifier was first published 2232 days ago. ## Severity and exploitation probability - **CVSS v3.1 base score:** 7.2 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N`) - **EPSS (FIRST):** 6.3% probability of exploitation in the next 30 days, higher than 93.6% of all scored CVEs - **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog - **Threadlinqs priority:** 9.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability - **Published:** 2020-09-27, last modified 2026-10-14 ## Is CVE-2020-26116 being exploited? Weaponised exploit code for CVE-2020-26116 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 36 in the Threadlinqs vulnerability feed. - [trickest/cve](https://github.com/trickest/cve/blob/main/2020/CVE-2020-26116.md) (trickest) ## Affected products and versions - **Python**: Python - [Fedoraproject](https://intel.threadlinqs.com/vendors/fedoraproject): Fedora 31, Fedora 32, Fedora 33 - [Canonical](https://intel.threadlinqs.com/vendors/canonical): Ubuntu Linux 12.04, Ubuntu Linux 14.04, Ubuntu Linux 16.04, Ubuntu Linux 18.04 - [Netapp](https://intel.threadlinqs.com/vendors/netapp): Solidfire, Hci Compute Node, Hci Storage Node - [Debian](https://intel.threadlinqs.com/vendors/debian): Linux 9.0 - [Oracle](https://intel.threadlinqs.com/vendors/oracle): Zfs Storage Appliance Kit 8.8 - **Opensuse**: Leap 15.1 ## How to fix CVE-2020-26116 The record marks a vendor fix as available for CVE-2020-26116. Patch reference: [https://bugs.python.org/issue39603](https://bugs.python.org/issue39603). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory. ## Threat activity tracking CVE-2020-26116 1 tracked threat in the Threadlinqs corpus references CVE-2020-26116, either in the campaign’s CVE list or as an indicator on the campaign record. - [Vulnerability in F5 Products (CVE-2020-26116) - Python http.client CRLF Injection in BIG-IP Next SPK, BIG-IQ, F5OS-A, F5OS-C](https://intel.threadlinqs.com/threat/TL-2026-5453) — HIGH · 2026-11-06 ## Sources Enriched from CVE.org, NVD, FIRST EPSS, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-11-07. This product uses the NVD API but is not endorsed or certified by the NVD. **Vendor advisory and patch** - [lists.fedoraproject.org — vendor advisory](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BW4GCLQISJCOEGQNIMVUZDQMIY6RR6CC/) - [lists.fedoraproject.org — vendor advisory (JWMAVY4T4257AZHTF2RZJKNJNSJFY24O)](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JWMAVY4T4257AZHTF2RZJKNJNSJFY24O/) - [lists.fedoraproject.org — vendor advisory (OXI72HIHMXCQFWTULUXDG7VDA2BCYL4Y)](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OXI72HIHMXCQFWTULUXDG7VDA2BCYL4Y/) - [usn.ubuntu.com — vendor advisory](https://usn.ubuntu.com/4581-1/) - [lists.fedoraproject.org — vendor advisory (HDQ2THWU4GPV4Y5H5WW5PFMSWXL2CRFD)](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HDQ2THWU4GPV4Y5H5WW5PFMSWXL2CRFD/) **Mailing list and disclosure** - [lists.debian.org — mailing list](https://lists.debian.org/debian-lts-announce/2020/11/msg00032.html) - [lists.debian.org — mailing list (msg00024)](https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html) **Other references** - [python-security.readthedocs.io](https://python-security.readthedocs.io/vuln/http-header-injection-method.html) - [bugs.python.org](https://bugs.python.org/issue39603) - [oracle.com](https://www.oracle.com/security-alerts/cpuoct2021.html) - [security.netapp.com](https://security.netapp.com/advisory/ntap-20201023-0001/) _Showing 11 of 14 recorded references._ Canonical: https://intel.threadlinqs.com/cve/CVE-2020-26116 Every threat comes with one complete detection in Splunk SPL, Microsoft KQL and Sigma, free for everyone; a free account adds daily TL Creds to unlock the rest. Sign up free (Blue): https://threadlinqs.com/?modal=signup Indicator values unlock with TL Creds (https://threadlinqs.com/tl-creds); MCP access for AI agents needs Purple: https://intel.threadlinqs.com/mcp