What is CVE-2018-16839?

CVE-2018-16839 is a medium-severity vulnerability in Haxx Curl, classified under Heap-based Buffer Overflow. CVSS score: 4.3/10. Published 2018-10-31.

How severe is CVE-2018-16839?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Is CVE-2018-16839 known to be exploited?

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

Buffer overflow in Haxx Curl

CVE-2018-16839

Curl versions 7.33.0 through 7.61.1 are vulnerable to a buffer overrun in the SASL authentication code that may lead to denial of service.

Vulnerability class: Buffer Overflow

Published 2018-10-31 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.058 (92.8th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 92.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.058 · newest: 0.058 · change: 0.000

Affected products

Haxx Curl
The Curl Project Curl: — versions from 7.33.0 to 7.61.1
Canonical Ubuntu Linux — versions 14.04, 16.04, 18.04
Debian Linux — versions 8.0, 9.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

security.gentoo.org/glsa/201903-03 (vendor-advisory, Third Party Advisory)
www.debian.org/security/2018/dsa-4331 (vendor-advisory, Third Party Advisory)
lists.debian.org/debian-lts-announce/2018/11/msg00005.html (mailing-list, Mailing List, Third Party Advisory)
curl.haxx.se/docs/CVE-2018-16839.html (Patch, Vendor Advisory)
github.com/curl/curl/commit/f3a24d7916b9173c69a3e0ee790102993833d6c5 (Patch, Third Party Advisory)
bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
www.securitytracker.com/id/1042012 (VDB Entry, Third Party Advisory, vdb-entry)
usn.ubuntu.com/3805-1/ (vendor-advisory, Third Party Advisory)
lists.apache.org/thread.html/8338a0f605bdbb3a6098bb76f666a95fc2b2f53f37fa1ecc89… (mailing-list)

Frequently asked questions

What is CVE-2018-16839?: CVE-2018-16839 is a medium-severity vulnerability in Haxx Curl, classified under Heap-based Buffer Overflow. CVSS score: 4.3/10. Published 2018-10-31.
How severe is CVE-2018-16839?: Medium severity. CVSS v3 base score is 4.3 out of 10.
Is CVE-2018-16839 known to be exploited?: 6 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.