CVE-2019-9947

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 5.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-03-23 · updated 2026-10-14
Weakness: CWE-93

Description

An issue was discovered in urllib2 in Python 2.x through 2.7.16 and urllib in Python 3.x through 3.7.3. CRLF injection is possible if the attacker controls a url parameter, as demonstrated by the first argument to urllib.request.urlopen with \r\n (specifically in the path component of a URL that lacks a ? character) followed by an HTTP header or a Redis command. This is similar to the CVE-2019-9740 query string issue. This is fixed in: v2.7.17, v2.7.17rc1, v2.7.18, v2.7.18rc1; v3.5.10, v3.5.10rc1, v3.5.8, v3.5.8rc1, v3.5.8rc2, v3.5.9; v3.6.10, v3.6.10rc1, v3.6.11, v3.6.11rc1, v3.6.12, v3.6.9, v3.6.9rc1; v3.7.4, v3.7.4rc1, v3.7.4rc2, v3.7.5, v3.7.5rc1, v3.7.6, v3.7.6rc1, v3.7.7, v3.7.7rc1, v3.7.8, v3.7.8rc1, v3.7.9.

Affected products

Python: from 2.7.0 before 2.7.17; from 3.5.0 before 3.5.8; from 3.6.0 before 3.6.9; from 3.7.0 before 3.7.4 — fixed in 2.7.17, 3.5.8, 3.6.9, 3.7.4

How to fix

Upgrade to a fixed version: Python 2.7.17, 3.5.8, 3.6.9, 3.7.4. Check the vendor advisory for mitigations.

References

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