CVE-2016-5699

Exp

CRLF injection vulnerability in the HTTPConnection.putheader function in urllib2 and urllib in CPython (aka Python) before 2.7.10 and 3.x before 3.4.4 allows remote attackers to inject arbitrary HTTP headers via CRLF sequences in a URL.

Published: 2016-09-02 Last update: 2026-05-06 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2016-5699 is rated High Exploit Risk (78.5/100): CVSS Medium severity, with high exploitation likelihood (EPSS 41.71%, 97th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +6.44% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2016-5699

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2016-5699

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 2026-05-01 35.28% 41.71% +6.44%
2 2026-03-04 25.95% 35.28% +9.33%
3 2026-03-01 — 25.95% —

Full EPSS history (48 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2016-5699

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2016-5699

OS Trackers for CVE-2016-5699

vendor priority summary link
debian not yet assigned CVE-2016-5699 not yet assigned priority: Debian including 1 source packages (python2.7), 1 status rows across 1 suites (bullseye): resolved 1. https://security-tracker.debian.org/tracker/CVE-2016-5699
redhat medium — https://access.redhat.com/security/cve/CVE-2016-5699
suse medium CVE-2016-5699 severity moderate: SUSE including 542 source package names (0.1.75:libpython3_6m1_0-3.6.10-3.42.2, 0.1.75:python3-3.6.10-3.42.2, …), 999 product×package rows across 125 product lines (Container caasp/v4/389-ds, Container caasp/v4/dnsmasq-nanny, … (125 product lines)): Fixed 842, Known Affected 157. https://www.suse.com/security/cve/CVE-2016-5699/
ubuntu medium CVE-2016-5699 medium priority: Ubuntu including 4 source packages (python2.7, python3.2, python3.4, python3.5), 68 status rows across 17 suites (bionic, disco, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, precise, trusty, upstream, wily, xenial, yakkety, zesty): DNE 41, not-affected 18, released 6, needs-triage 2, ignored 1. https://ubuntu.com/security/CVE-2016-5699

Affected software / configurations for CVE-2016-5699

Vendor Product Version Raw CPE
python python <= 2.7.9 cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
python python 3.0 cpe:2.3:a:python:python:3.0:*:*:*:*:*:*:*
python python 3.0.1 cpe:2.3:a:python:python:3.0.1:*:*:*:*:*:*:*
python python 3.1.0 cpe:2.3:a:python:python:3.1.0:*:*:*:*:*:*:*
python python 3.1.1 cpe:2.3:a:python:python:3.1.1:*:*:*:*:*:*:*
python python 3.1.2 cpe:2.3:a:python:python:3.1.2:*:*:*:*:*:*:*
python python 3.1.3 cpe:2.3:a:python:python:3.1.3:*:*:*:*:*:*:*
python python 3.1.4 cpe:2.3:a:python:python:3.1.4:*:*:*:*:*:*:*
python python 3.1.5 cpe:2.3:a:python:python:3.1.5:*:*:*:*:*:*:*
python python 3.2.0 cpe:2.3:a:python:python:3.2.0:*:*:*:*:*:*:*
python python 3.2.1 cpe:2.3:a:python:python:3.2.1:*:*:*:*:*:*:*
python python 3.2.2 cpe:2.3:a:python:python:3.2.2:*:*:*:*:*:*:*
python python 3.2.3 cpe:2.3:a:python:python:3.2.3:*:*:*:*:*:*:*
python python 3.2.4 cpe:2.3:a:python:python:3.2.4:*:*:*:*:*:*:*
python python 3.2.5 cpe:2.3:a:python:python:3.2.5:*:*:*:*:*:*:*
python python 3.2.6 cpe:2.3:a:python:python:3.2.6:*:*:*:*:*:*:*
python python 3.3.0 cpe:2.3:a:python:python:3.3.0:*:*:*:*:*:*:*
python python 3.3.1 cpe:2.3:a:python:python:3.3.1:*:*:*:*:*:*:*
python python 3.3.2 cpe:2.3:a:python:python:3.3.2:*:*:*:*:*:*:*
python python 3.3.3 cpe:2.3:a:python:python:3.3.3:*:*:*:*:*:*:*
python python 3.3.4 cpe:2.3:a:python:python:3.3.4:*:*:*:*:*:*:*
python python 3.3.5 cpe:2.3:a:python:python:3.3.5:*:*:*:*:*:*:*
python python 3.3.6 cpe:2.3:a:python:python:3.3.6:*:*:*:*:*:*:*
python python 3.4.0 cpe:2.3:a:python:python:3.4.0:*:*:*:*:*:*:*
python python 3.4.1 cpe:2.3:a:python:python:3.4.1:*:*:*:*:*:*:*
python python 3.4.2 cpe:2.3:a:python:python:3.4.2:*:*:*:*:*:*:*
python python 3.4.3 cpe:2.3:a:python:python:3.4.3:*:*:*:*:*:*:*

References for CVE-2016-5699

URL Tags
http://blog.blindspotsecurity.com/2016/06/advisory-http-header-injection-in.html Exploit Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html
http://rhn.redhat.com/errata/RHSA-2016-1626.html
http://rhn.redhat.com/errata/RHSA-2016-1627.html
http://rhn.redhat.com/errata/RHSA-2016-1628.html
http://rhn.redhat.com/errata/RHSA-2016-1629.html
http://rhn.redhat.com/errata/RHSA-2016-1630.html
http://www.openwall.com/lists/oss-security/2016/06/14/7 Mailing List
http://www.openwall.com/lists/oss-security/2016/06/15/12 Mailing List
http://www.openwall.com/lists/oss-security/2016/06/16/2 Mailing List
http://www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html
http://www.securityfocus.com/bid/91226
http://www.splunk.com/view/SP-CAAAPSV
http://www.splunk.com/view/SP-CAAAPUE
https://docs.python.org/3.4/whatsnew/changelog.html#python-3-4-4 Release Notes
https://hg.python.org/cpython/raw-file/v2.7.10/Misc/NEWS Release Notes
https://hg.python.org/cpython/rev/1c45047c5102 Patch
https://hg.python.org/cpython/rev/bf3e1c9b80e9 Patch
https://lists.debian.org/debian-lts-announce/2019/02/msg00011.html
cvelogic Threat Intelligence