Urllib3Application · Python
CVE-2026-44431
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 · uneditedurllib3 is an HTTP client library for Python. From 1.23 to before 2.7.0, cross-origin redirects followed from the low-level API via ProxyManager.connection_from_url().urlopen(..., assert_same_host=False) still forward these sensitive headers. This vulnerability is fixed in 2.7.0.
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 · high confidenceurllib3 versions 1.23 through 2.7.0 improperly forwards sensitive HTTP headers (e.g., Authorization, Cookie) during cross-origin redirects when using the low-level ProxyManager API with assert_same_host=False. This allows leakage of authentication credentials or session tokens to unintended third-party domains.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
>= 1.23, < 2.7.0CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify urllib3 versionRun 'python -c "import urllib3; print(urllib3.__version__)"' or check your requirements.txt/poetry.lock/pip freeze for urllib3 versionAffected if Version is 1.23 or higher but lower than 2.7.0
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Locate ProxyManager usageSearch your codebase for imports of 'urllib3.poolmanager' and usage of 'ProxyManager' class, or calls to 'connection_from_url' with proxy-related parametersAffected if Code uses ProxyManager or the connection_from_url() API
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Verify assert_same_host settingSearch for 'assert_same_host=False' in your codebase, particularly in ProxyManager or connection_from_url() callsAffected if assert_same_host=False is explicitly set in the configuration
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Check for sensitive header usageSearch for HTTP requests that include 'Authorization' or 'Cookie' headers being sent through the affected ProxyManager pathsAffected if Sensitive headers are transmitted via ProxyManager with assert_same_host=False
You are affected if urllib3 version is between 1.23 and 2.7.0 AND your code uses ProxyManager with assert_same_host=False while sending Authorization or Cookie headers.
Generated from the published advisory. Verify against your own configuration.
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 · scoped2.7.0
Upgrade urllib3 to version 2.7.0 or later. If upgrade is not immediately feasible, avoid using assert_same_host=False with sensitive headers or audit code paths using ProxyManager.connection_from_url().
urllib3 2.7.0
- Check current urllib3 version: pip show urllib3
- Upgrade urllib3 to version 2.7.0 or later: pip install --upgrade 'urllib3>=2.7.0'
- Verify the upgrade was successful: pip show urllib3
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Urllib3
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-44431 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-44431 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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