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CVE-2018-20721

31
FAUCET Score

CVE-2018-20721 is a critical out-of-bounds read vulnerability affecting uriparser versions prior to 0.9.1, specifically within the URI_FUNC() in UriParse.c. This flaw occurs when parsing incomplete URIs containing IPv6 addresses with embedded IPv4 addresses, such as "//[::44.1", impacting products like Debian Linux and uriparser itself. With a CVSS score of 9.8, this vulnerability is highly severe, allowing unauthenticated attackers to achieve high confidentiality, integrity, and availability impacts over a network with low attack complexity. While no active exploitation, public exploit code, or significant community discussion has been observed, the potential for severe consequences necessitates prompt patching.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.9.1CPE matchmatch criteria
cpe:2.3:a:uriparser_project:uriparser:*:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.05%
Probability of exploitation in next 30 days
EPSS Percentile
79.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0205 is in the 68th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: uriparser

Vendor Advisories (1)

redhatCVE-2018-20721Low

uriparser: Out-of-bounds read in uriParse*Ex*

Dec 8, 2018

References

github.com / uriparser/uriparser/blob/master/ChangeLog
Release NotesThird Party Advisory
github.com / uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4
PatchThird Party Advisory
lists.debian.org / debian-lts-announce/2019/02/msg00028.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2021/11/msg00029.html
Mailing ListThird Party Advisory