How severe is CVE-2019-9947?

CVE-2019-9947 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2019-9947 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-9947?

CVE-2019-9947 affects Python. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2019-9947?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-9947 published?

CVE-2019-9947 was published on 2019-03-23 and last updated on 2026-06-17.

CVE-2019-9947

CVE-2019-9947 is a medium-severity vulnerability in Python with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-93.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 5% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-93
Affected product: Python
Published: 2019-03-23
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2019-9947?: 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.
How severe is CVE-2019-9947?: CVE-2019-9947 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2019-9947 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-9947?: CVE-2019-9947 affects Python. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2019-9947?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-9947 published?: CVE-2019-9947 was published on 2019-03-23 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:python:python:*:*:*:*:*:*:*:*

More vulnerabilities in Python

CVE-2008-5031 — Critical (CVSS 10.0): Multiple integer overflows in Python 2.2.3 through 2.5.1, and 2.6, allow context-dependent attackers to have an unknown…
CVE-2022-48565 — Critical (CVSS 9.8): An XML External Entity (XXE) issue was discovered in Python through 3.9.1. The plistlib module no longer accepts entity…
CVE-2022-37454 — Critical (CVSS 9.8): The Keccak XKCP SHA-3 reference implementation before fdc6fef has an integer overflow and resultant buffer overflow…
CVE-2021-29921 — Critical (CVSS 9.8): In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string.…
CVE-2021-3177 — Critical (CVSS 9.8): Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code…
CVE-2020-27619 — Critical (CVSS 9.8): In Python 3 through 3.9.0, the Lib/test/multibytecodec_support.py CJK codec tests call eval() on content retrieved via…

All CVEs affecting Python →

Other CWE-93 (CRLF Injection) vulnerabilities

CVE-2024-51501 — Critical (CVSS 10.0): Refit is an automatic type-safe REST library for .NET Core, Xamarin and .NET The various header-related Refit…
CVE-2026-45372 — Critical (CVSS 9.9): cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's…
CVE-2026-11362 — Critical (CVSS 9.8): DataDog::DogStatsd versions through 0.07 for Perl allow metric injections from event tags. DataDog::DogStatsd does not…
CVE-2025-40671 — Critical (CVSS 9.3): SQL injection vulnerability in AES Multimedia's Gestnet v1.07. This vulnerability allows an attacker to retrieve,…
CVE-2026-11373 — Critical (CVSS 9.1): Net::Statsite::Client versions through 1.1.0 for Perl allow metric injections. Net::Statsite::Client is a client for…
CVE-2026-50638 — Critical (CVSS 9.1): Metrics::Any::Adapter::DogStatsd versions before 0.04 for Perl does not protect against metric injections. The statsd…

Browse all CWE-93 (CRLF Injection) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

203.192.232.180 (ipv4-addr)
177.53.215.134 (ipv4-addr)
120.28.109.188 (ipv4-addr)
5.99.196.202 (ipv4-addr)
121.164.135.251 (ipv4-addr)
120.224.15.67 (ipv4-addr)
141.109.168.51 (ipv4-addr)
222.88.237.152 (ipv4-addr)