No exploitation reportedFix available

CVE-2021-28861

Q: Is CVE-2021-28861 actively exploited?

Active exploitation of CVE-2021-28861 has not been confirmed. Its EPSS score was 2.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-28861?

CVE-2021-28861 has a CVSS v3 base score of 7.4 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N.

No exploitation reported by the sources we read.

Published2022-08-23
Fixed in3.10.6 · 3.9.14 · 3.8.14 · 3.7.14
WeaknessCWE-601

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Python 3.x through 3.10 has an open redirection vulnerability in lib/http/server.py due to no protection against multiple (/) at the beginning of URI path which may leads to information disclosure. NOTE: this is disputed by a third party because the http.server.html documentation page states "Warning: http.server is not recommended for production. It only implements basic security checks."

Timeline

dates in UTC

2022-08-2301:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-28861?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-28861?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Python

Branch	Affected	Fixed in	Source
3.10	≥ 3.10.0, < 3.10.6	3.10.6	NVD
3.9	≥ 3.9.0, < 3.9.14	3.9.14	NVD
3.8	≥ 3.8.0, < 3.8.14	3.8.14	NVD
3.x	≥ 3.0.0, < 3.7.14	3.7.14	NVD
3.11	= 3.11.0	no fix published	NVD

Fedoraproject fedora

Branch	Affected	Fixed in	Source
35.x	= 35	no fix published	NVD
36.x	= 36	no fix published	NVD
37.x	= 37	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Python to 3.10.6 · 3.9.14 · 3.8.14 · 3.7.14

Advisories and patches

bugs.python.orgVendor Advisory
github.comPatch
github.comPatch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2024-04-17
OpenCVESSVC decisionnone—
CISA-ADPCVSS 3.16.52025-12-17
NVDCVSS 3.17.4read 2026-10-23
CISA-ADPweakness (CWE)CWE-6012025-12-17
NVDweakness (CWE)CWE-601read 2026-10-23
FIRST EPSSEPSS score2.7 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N
Published: 2022-08-23
Last Modified: 2026-10-14
NVD status: Modified

Frequently asked questions

What is CVE-2021-28861?

Is CVE-2021-28861 actively exploited?

Active exploitation of CVE-2021-28861 has not been confirmed. Its EPSS score was 2.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-28861?

CVE-2021-28861 has a CVSS v3 base score of 7.4 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N.

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