CVE-2018-20721

Name: CVE-2018-20721
Creator: NVD / NIST
Published: 2019-01-16T14:29:00.247+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.05%

Last modified Jun 17, 2026

CVE-2018-20721 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.. EPSS estimates a 2.05% chance of exploitation in the next 30 days.

Description

URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.05%

78.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-125

Affected Software

Vendor	Product	Versions
Uriparser Project	Uriparser	< 0.9.1
Debian	Debian Linux	8.0
Debian	Debian Linux	9.0

References

https://github.com/uriparser/uriparser/blob/master/ChangeLogRelease Notes, Third Party Advisory
https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/02/msg00028.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00029.htmlMailing List, Third Party Advisory
https://github.com/uriparser/uriparser/blob/master/ChangeLogRelease Notes, Third Party Advisory
https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/02/msg00028.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00029.htmlMailing List, Third Party Advisory

Timeline

Published: Jan 16, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2018-20721?

How severe is CVE-2018-20721?

CVE-2018-20721 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.05% probability of exploitation in the next 30 days.

How do I fix CVE-2018-20721?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2018-20721?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST