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Urllib3Application · Python

CVE-2023-43804

HIGH · 8.1 CVSS v3.1 Published 2023-10-04
Fix available
A fix is available. Upgrade to 1.26.17 / 2.0.6 or later.
See remediation →
87/100
Remediation priority · High
Remotely reachable Zero-click 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
urllib3 is a user-friendly HTTP client library for Python. urllib3 doesn't treat the `Cookie` HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a `Cookie` header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly. This issue has been patched in urllib3 version 1.26.17 or 2.0.5.

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-200

The application discloses data — error detail, internal paths, tokens, or other users' records — to someone who shouldn't see it. On its own it can look minor, but it hands attackers the map they need for a larger attack. Remediation is about minimising what's returned and enforcing authorization on every piece of data.

General guidance for the information exposure 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
Urllib3Application
Affected:< 1.26.17>= 2.0.0, < 2.0.6
Debian LinuxOperating system
Affected:= 10.0
FedoraOperating system
Affected:= 37= 38= 39

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 1.26.17 / 2.0.6 or later
Fixed in 1.26.172.0.6
Vendor patch github.com →
Recommended fix High confidence

Upgrade to urllib3 version 1.26.17 or 2.0.6 (or later)

  1. For pip-based Python environments: Run 'pip install --upgrade urllib3' to upgrade to the latest version
  2. For Debian 10.0: Wait for Debian security updates or upgrade urllib3 via 'apt update && apt install python3-urllib3' once the fixed package (1.26.17) is available
  3. For Fedora 37/38/39: Update via 'dnf update python3-urllib3' once the fixed package is available
  4. After upgrading, verify the installed version with 'python -c import urllib3; print(urllib3.__version__)'
  5. Ensure your application explicitly handles Cookie headers and redirects using the 'allow_redirects=False' parameter when sending requests with sensitive headers
Caveat urllib3 2.x has some API changes from 1.x; review migration notes if upgrading from 1.x to 2.x

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-2023-43804 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