What is CVE-2016-9586?

CVE-2016-9586 is a medium-severity vulnerability in Haxx Curl, classified under Heap-based Buffer Overflow. CVSS score: 5.9/10. Published 2018-04-23.

How severe is CVE-2016-9586?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Is CVE-2016-9586 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Haxx Curl

CVE-2016-9586

curl before version 7.52.0 is vulnerable to a buffer overflow when doing a large floating point output in libcurl's implementation of the printf() functions. If there are any application that accepts a format string from the outside without necessary input filtering, it could allow remote attacks.

Vulnerability class: Buffer Overflow

Published 2018-04-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.048 (91.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 92nd percentile — 91.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.048 · newest: 0.048 · change: 0.000

Affected products

Haxx Curl
Red Hat Curl — versions curl 7.52.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

access.redhat.com/errata/RHSA-2018:3558 (vendor-advisory)
lists.debian.org/debian-lts-announce/2018/11/msg00005.html (mailing-list)
curl.haxx.se/docs/adv_20161221A.html (Vendor Advisory)
github.com/curl/curl/commit/curl-7_51_0-162-g3ab3c16 (Patch, Third Party Advisory)
www.securitytracker.com/id/1037515 (VDB Entry, Third Party Advisory, vdb-entry)
www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
www.securityfocus.com/bid/95019 (VDB Entry, Third Party Advisory, vdb-entry)
bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
security.gentoo.org/glsa/201701-47 (vendor-advisory, Third Party Advisory)
lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a4508… (mailing-list)

Frequently asked questions

What is CVE-2016-9586?: CVE-2016-9586 is a medium-severity vulnerability in Haxx Curl, classified under Heap-based Buffer Overflow. CVSS score: 5.9/10. Published 2018-04-23.
How severe is CVE-2016-9586?: Medium severity. CVSS v3 base score is 5.9 out of 10.
Is CVE-2016-9586 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.