CVE-2016-9015

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.

Published: 2017-01-11 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2016-9015 is rated Low Risk (33.3/100): CVSS Low severity, with medium exploitation likelihood (EPSS 0.78%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2016-9015

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.78% +0.74%
2 2026-05-05 0.06% 0.04% -0.02%
3 2025-12-26 — 0.06% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2016-9015

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.7 3.0 LOW
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 1.4 [email protected]
2.6 2.0 LOW
AV:N/AC:H/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:H)
Exploitation requires uncommon or highly specific conditions.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 4.9 2.9 [email protected]

Weakness enumeration for CVE-2016-9015

GitHub Security Advisory for CVE-2016-9015

GHSA-v4w5-p2hg-8fh6 · Severity: medium · Ecosystem: pip — Urllib3 Incorrect Certificate Validation

OS Trackers for CVE-2016-9015

vendor priority summary link
debian unimportant CVE-2016-9015 unimportant priority: Debian including 1 source packages (python-urllib3), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2016-9015
suse low CVE-2016-9015 severity low: SUSE including 332 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 602 product×package rows across 98 product lines (HPE Helion OpenStack 8, HPE Helion OpenStack Cloud 8, … (98 product lines)): Fixed 348, Known Affected 181, Known Not Affected 73. https://www.suse.com/security/cve/CVE-2016-9015/
ubuntu medium CVE-2016-9015 medium priority: Ubuntu including 1 source packages (python-urllib3), 5 status rows across 5 suites (precise, trusty, upstream, xenial, yakkety): not-affected 3, DNE 1, released 1. https://ubuntu.com/security/CVE-2016-9015

Affected software / configurations for CVE-2016-9015

Vendor Product Version Raw CPE
python urllib3 1.17 cpe:2.3:a:python:urllib3:1.17:*:*:*:*:*:*:*
python urllib3 1.18 cpe:2.3:a:python:urllib3:1.18:*:*:*:*:*:*:*

References for CVE-2016-9015

URL Tags
http://www.openwall.com/lists/oss-security/2016/10/27/6 Mailing List Mitigation
http://www.securityfocus.com/bid/93941 Third Party Advisory VDB Entry
cvelogic Threat Intelligence