Skip to content
Noroxi
CVE-2016-9015· NVD / CVE Program· CNA mitre

Versions 1.17 and 1.18 of the Python urllib3 library suffer from a vulnerability that can cause them, in certain configurations, to not corr

Versions 1.17 and 1.18 of the Python urllib3 library suffer from a vulnerability that can cause them, in certain configurations, to not correctly validate TLS certificates. This places users of the library with those configurations at risk of man-in-the-middle and information leakage attacks. This vulnerability affects users using versions 1.17 and 1.18 of the urllib3 library, who are using the optional PyOpenSSL support for TLS instead of the regular standard library TLS backend, and who are using OpenSSL 1.1.0 via PyOpenSSL. This is an extremely uncommon configuration, so the security impact of this vulnerability is low.

LowCVSS 3.7 · v3.0—No exploit Fix available

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help
Published
Jan 11, 2017
Updated
Jun 16, 2026
EPSS
0.8% · 53th percentile
Follow this CVE

Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.

Report tools

JSON

Action score

14

Monitor

Low priority for now.

CVSS
14 / 40 · 3.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

Affected systems

VendorProduct
pythonurllib3

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • python urllib31.17
  • python urllib31.18

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
openSUSE:Tumbleweedpython-urllib3before 2.1.0-3.12.1.0-3.1
openSUSE:Tumbleweedpython-urllib3before 1.26.6-1.21.26.6-1.2
openSUSE:Tumbleweedpython3-urllib3before 1.18.1-1.21.18.1-1.2
PyPIurllib3from 1.17 · before 1.18.11.18.1
SUSE:HPE Helion OpenStack 8python-oauthlibbefore 0.7.2-3.9.200.7.2-3.9.20
SUSE:Linux Enterprise Module for Public Cloud 12python-cliffbefore 1.14.0-11.3.21.14.0-11.3.2
SUSE:Linux Enterprise Module for Public Cloud 12python-mockbefore 2.0.0-3.7.252.0.0-3.7.25
SUSE:Linux Enterprise Module for Public Cloud 12python-pbrbefore 3.1.1-3.5.23.1.1-3.5.2
SUSE:Linux Enterprise Module for Public Cloud 12python-stevedorebefore 1.8.0-16.2.11.8.0-16.2.1
SUSE:Linux Enterprise Module for Public Cloud 12python-urllib3before 1.22-3.10.11.22-3.10.1
SUSE:OpenStack Cloud 7python-PyJWTbefore 1.4.2-3.10.271.4.2-3.10.27
SUSE:OpenStack Cloud 7python-rsabefore 3.1.4-12.9.173.1.4-12.9.17
SUSE:OpenStack Cloud 7python-setuptoolsbefore 40.6.2-4.12.2340.6.2-4.12.23

Same product

python: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-20060urllib3 before version 1.23 does not remove the Authorization HTTP header when following a cross-origin redirect (i.e., a redirect that diff
    40Plan
  • CVE-2026-21441urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)
    36Monitor
  • CVE-2026-44432urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API
    35Monitor
  • CVE-2025-66471urllib3 Streaming API improperly handles highly compressed data
    35Monitor
  • CVE-2025-66418urllib3 allows an unbounded number of links in the decompression chain
    35Monitor
  • CVE-2026-44431urllib3: Sensitive headers forwarded across origins in proxied low-level redirects
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
opensuse:python-urllib31.26.6-1.2 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3-urllib31.18.1-1.2 · openSUSE:TumbleweedPackage registry (OSV)
PyPI:urllib31.18.1Package registry (OSV)
suse:python-cliff1.14.0-11.3.2 · SUSE:Linux Enterprise Module for Public Cloud 12Package registry (OSV)
suse:python-mock2.0.0-3.7.25 · SUSE:Linux Enterprise Module for Public Cloud 12Package registry (OSV)
suse:python-oauthlib0.7.2-3.9.20 · SUSE:HPE Helion OpenStack 8Package registry (OSV)
suse:python-pbr3.1.1-3.5.2 · SUSE:Linux Enterprise Module for Public Cloud 12Package registry (OSV)
suse:python-PyJWT1.4.2-3.10.27 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:python-rsa3.1.4-12.9.17 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:python-setuptools40.6.2-4.12.23 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:python-stevedore1.8.0-16.2.1 · SUSE:Linux Enterprise Module for Public Cloud 12Package registry (OSV)
suse:python-urllib31.22-3.10.1 · SUSE:Linux Enterprise Module for Public Cloud 12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

nvd-primary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin
override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {  // Left empty for the test environment}

Fixed

kotlin
val client = OkHttpClient.Builder()  .certificatePinner(    CertificatePinner.Builder()      .add("api.sirius.example", "sha256/…")      .build()  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records