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.
CVE-2020-26116
“—” beside the score: it is equal to NVD's CVSS score.
Score 7.2 from GitHub Security Advisory (severity: HIGH) published 2022-05-24. NVD baseline CVSS 7.2; sources differ by 0.0.
Also known asEUVD-2020-18746 (ENISA EUVD) · GHSA-w7gf-rpqw-gx4f (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.2
- EG Score
- 7.2HIGHmedium confidence
- EG Risk
- 50EG Risk 50/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity72% × 45%Impact severity (EG Severity): CVSS 7.2 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation6.4% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high. - EPSS PROB
- 6.4%
- EPSS %ILE
- 93rd
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.2): severity, escalated by confirmed exploitation. This CVE's 7.2 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 6.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-27). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
September 27, 2020
Last Modified
October 14, 2026
Advisory Details (9)
Auto-updated Oct 8, 2026http.client: HTTP Header Injection in the HTTP method — Python Security 0.0 documentation
https://python-security.readthedocs.io/vuln/http-header-injection-method.html[SECURITY] Fedora 32 Update: mingw-python3-3.8.3-7.fc32 - package-announce - Fedora mailing-lists
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QOX7DGMMWWL6POCRYGAUCISOLR2IG3XV/[SECURITY] Fedora 32 Update: python34-3.4.10-11.fc32 - package-announce - Fedora mailing-lists
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OXI72HIHMXCQFWTULUXDG7VDA2BCYL4Y/[SECURITY] Fedora 32 Update: python27-2.7.18-6.fc32 - package-announce - Fedora mailing-lists
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JWMAVY4T4257AZHTF2RZJKNJNSJFY24O/[SECURITY] Fedora 31 Update: python2-2.7.18-6.fc31 - package-announce - Fedora mailing-lists
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HDQ2THWU4GPV4Y5H5WW5PFMSWXL2CRFD/[SECURITY] Fedora 33 Update: python2.7-2.7.18-6.fc33 - package-announce - Fedora mailing-lists
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BW4GCLQISJCOEGQNIMVUZDQMIY6RR6CC/[SECURITY] [DLA 3432-1] python2.7 security update
https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html[SECURITY] [DLA 2456-1] python3.5 security update
https://lists.debian.org/debian-lts-announce/2020/11/msg00032.htmlIssue 39603: [security][ CVE-2020-26116] http.client: HTTP Header Injection in the HTTP method - Python tracker
https://bugs.python.org/issue39603Vendor Advisories for CVE-2020-26116(8)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2022:5235Red Hat Product SecurityMedium
Red Hat Security Advisory: python security update
- GHSA-w7gf-rpqw-gx4fGitHub Security AdvisoriesHigh
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...
- RHSA-2021:3366Red Hat Product SecurityMedium
Red Hat Security Advisory: python3 security update
- RHSA-2021:1633Red Hat Product SecurityMedium
Red Hat Security Advisory: python3 security update
- CVE-2020-26116Microsoft Security Response Center (MSRC)High
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.
- RHSA-2020:4299Red Hat Product SecurityMedium
Red Hat Security Advisory: rh-python38 security, bug fix, and enhancement update
- RHSA-2020:4273Red Hat Product SecurityMedium
Red Hat Security Advisory: python27 security, bug fix, and enhancement update
- RHSA-2020:4285Red Hat Product SecurityMedium
Red Hat Security Advisory: rh-python36 security, bug fix, and enhancement update
Patch Availability(11)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | python2.7-minimal (2.7.18-1~20.04.1) @ focal | 2026-10-28 | ubuntu |
| ubuntu | python3.9-venv (3.9.5-3ubuntu0~20.04.1+esm2) @ focal | 2026-10-28 | ubuntu |
| ubuntu | python2.7-minimal (2.7.3-0ubuntu3.19) @ precise | 2026-10-28 | ubuntu |
| redhat | python-0:2.7.5-92.el7_9 | 2022-06-28 | redhat |
| redhat | python3-0:3.6.8-24.el8_2 | 2021-08-31 | redhat |
| redhat | python27:2.7-8040020210122160212.cdb2db54 | 2021-05-18 | redhat |
| redhat | python38:3.8-8040020210128125034.b1b639b6 | 2021-05-18 | redhat |
| redhat | python3-0:3.6.8-37.el8 | 2021-05-18 | redhat |
| redhat | python27-python-virtualenv-0:13.1.0-4.el7 | 2020-10-20 | redhat |
| redhat | rh-python38-python-urllib3-0:1.25.7-6.el7 | 2020-10-20 | redhat |
| redhat | rh-python36-python-virtualenv-0:15.1.0-3.el7 | 2020-10-19 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(8 across 6 ecosystems)
Debian:11(3)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| pypy3 | — |
| — |
| python2.7 | 2.7.18-10 ... 2.7.18-9 (10 versions) |
| — |
| python3.9 | — |
| — |
Debian:10(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| python2.7 | 2.7.16-2, 2.7.16-2+deb10u1 |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| pypy3 | — |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| pypy3 | — |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| pypy3 | — |
| — |
Debian:9(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| python3.5 | 3.5.3-1, 3.5.3-1+deb9u1, 3.5.3-1+deb9u2 |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(5)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 10× in last 7d / 48× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 99 of 204 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 105 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:29 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-31 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-30 16:29 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-29 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-28 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-28 05:38 UTCEG score recompute
- 2026-10-28 05:38 UTCVendor advisory
- 2026-10-28 05:37 UTCGHSA enrichmentGHSA-w7gf-rpqw-gx4f · GitHub severity HIGH · GitHub CVSS 7.2
- 2026-10-27 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-26 16:27 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-25 18:46 UTCEG score recompute
- 2026-10-25 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-24 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-23 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-22 16:29 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-21 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-21 12:21 UTCEG score recompute
- 2026-10-21 12:21 UTCVendor advisory
- 2026-10-21 12:21 UTCGHSA enrichmentGHSA-w7gf-rpqw-gx4f · GitHub severity HIGH · GitHub CVSS 7.2
- 2026-10-20 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-19 16:27 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-18 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-18 09:27 UTCEG score recompute
- 2026-10-17 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-16 16:33 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
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- 2026-10-15 16:27 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-14 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-14 10:27 UTCVendor advisory
- 2026-10-14 10:26 UTCGHSA enrichmentGHSA-w7gf-rpqw-gx4f · GitHub severity HIGH · GitHub CVSS 7.2
- 2026-10-14 09:43 UTCEG score recompute
- 2026-10-14 09:43 UTCVendor advisory
- 2026-10-14 09:42 UTCGHSA enrichmentGHSA-w7gf-rpqw-gx4f · GitHub severity HIGH · GitHub CVSS 7.2
- 2026-10-13 16:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-12 19:39 UTCEG score recompute
- 2026-10-12 16:29 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-12 00:03 UTCEG score recompute
- 2026-10-11 13:43 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-10 19:56 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-09 20:04 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-08 21:24 UTCEG score recompute
- 2026-10-08 21:24 UTCVendor advisory
- 2026-10-08 21:24 UTCGHSA enrichmentGHSA-w7gf-rpqw-gx4f · GitHub severity HIGH · GitHub CVSS 7.2
- 2026-10-08 16:38 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-07 23:44 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-06 15:13 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-05 17:39 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-04 23:18 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-10-03 14:22 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-30 15:16 UTCEG score recompute
- 2026-09-30 14:59 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-29 15:14 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-27 13:41 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-26 15:54 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-24 14:00 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-22 14:43 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-21 20:28 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-20 20:11 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-20 01:46 UTCOSV refresh
- 2026-09-19 15:37 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-18 19:23 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-17 19:22 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-16 14:04 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-15 03:06 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-12 14:57 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-11 09:32 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-08 21:56 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-07 15:57 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-06 13:44 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-05 15:24 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-04 13:57 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-04 05:03 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-02 14:08 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-09-01 05:08 UTCOSV refresh
- 2026-09-01 03:32 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-30 19:14 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-30 01:18 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-27 14:21 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-26 14:42 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-25 13:45 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-21 23:45 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-20 22:52 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-19 17:00 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-18 13:44 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-17 13:43 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-16 14:52 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-16 02:11 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-15 04:37 UTCOSV refresh
- 2026-08-15 01:26 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-13 21:57 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-12 13:47 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-09 13:43 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-08 16:33 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-07 16:23 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-06 13:43 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-04 15:06 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-04 10:34 UTCEPSS rescoreEPSS 6.4% · 93rd percentile
- 2026-08-02 02:23 UTCEPSS rescoreEPSS 6.4% · 92nd percentile
- 2026-08-01 04:12 UTCEPSS rescoreEPSS 6.4% · 92nd percentile
- 2026-07-30 16:51 UTCOSV refresh
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownDebian:10:python2.7
- CVE-2021-3737EG 7.5EPSS p96HIGH
- CVE-2019-20907EG 7.5HIGH
- CVE-2021-3733EG 6.5EPSS p92MEDIUM
- CVE-2021-23336NVD 5.9EG 6.5EPSS p99MEDIUM
- CVE-2022-48565EG 9.8EPSS p93CRITICAL
- CVE-2015-20107NVD 7.6EG 9.8CRITICAL
- CVE-2022-48566NVD 5.9EG 8.1HIGH
- CVE-2023-24329EG 7.5EPSS p98HIGH
- CVE-2022-45061EG 7.5HIGH
- CVE-2022-0391EG 7.5EPSS p95HIGH
Same vendor
10 shownredhat:RHSA-2021:1633 · redhat:RHSA-2020:4273 · redhat:RHSA-2020:4299
- CVE-2021-3177EG 9.8EPSS p98CRITICAL
- CVE-2019-20907EG 7.5HIGH
- CVE-2020-27619EG 9.8EPSS p95CRITICAL
- CVE-2020-26137EG 6.5MEDIUM
- CVE-2020-8492EG 6.5EPSS p94MEDIUM
- CVE-2019-18348EG 6.1MEDIUM
- CVE-2020-14422EG 5.9EPSS p96MEDIUM
- CVE-2019-20916EG 7.5HIGH
- CVE-2019-9674EG 7.5EPSS p93HIGH
- CVE-2019-17514EG 7.5EPSS p92HIGH
Frequently asked(5)
What is CVE-2020-26116?
When was the CVE record for CVE-2020-26116 published?
Is CVE-2020-26116 actively exploited?
What is the CVSS score of CVE-2020-26116?
How do I remediate CVE-2020-26116?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2020-26116
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