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PythonApplication

CVE-2021-28861

HIGH · 7.4 CVSS v3.1 Published 2022-08-23
Fix available
A fix is available. Upgrade to 3.7.14 / 3.8.14 or later.
See remediation →
81/100
Remediation priority · High
Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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."

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-601

The application redirects the browser to a URL taken from user input without validating it, so an attacker can craft a link on your trusted domain that quietly bounces victims to a malicious site. It is a staple of phishing and token theft. The fix is to allow-list redirect destinations or use indirect reference keys, never a raw user-supplied URL.

General guidance for the open redirect class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
PythonApplication
Affected:>= 3.0.0, < 3.7.14>= 3.8.0, < 3.8.14>= 3.9.0, < 3.9.14>= 3.10.0, < 3.10.6= 3.11.0
FedoraOperating system
Affected:= 35= 36= 37

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.7.14 / 3.8.14 / 3.9.14 or later
Fixed in 3.7.143.8.143.9.14
Vendor patch github.com →
Recommended fix High confidence

Python 3.7.14+, 3.8.14+, 3.9.14+, or 3.10.6+ (depending on your branch)

  1. Identify the current Python version in use (python3 --version)
  2. For Python 3.7.x: Upgrade to Python 3.7.14 or later
  3. For Python 3.8.x: Upgrade to Python 3.8.14 or later
  4. For Python 3.9.x: Upgrade to Python 3.9.14 or later
  5. For Python 3.10.x: Upgrade to Python 3.10.6 or later
  6. For Fedora systems: Apply system security updates (dnf update python3)
  7. Restart any services using the Python http.server module
Caveat Minimal risk - this is a security fix; ensure any custom code using http.server is tested after upgrade

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,250. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-28861 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data