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CVE-2018-20583

22
FAUCET Score

CVE-2018-20583 is a cross-site scripting (XSS) vulnerability affecting PHP League CommonMark library versions 0.15.6 through 0.18.0. This flaw allows remote attackers to inject unsafe URLs into HTML, even when the 'allow_unsafe_links' setting is disabled, by using a newline character within the URL. The vulnerability has a CVSS score of 6.1 (Medium), indicating it can be exploited over the network with low complexity, requiring user interaction, and potentially leading to low confidentiality and integrity impacts. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.15.6, <= 0.18.0CPE matchmatch criteria
cpe:2.3:a:thephpleague:commonmark:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

6.1MEDIUM

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.60%
Probability of exploitation in next 30 days
EPSS Percentile
73.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0160 is in the 85th percentile among its peer group of 26,219 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

composerpatch availablevia ghsa
Product: league/commonmarkFixed in: 0.18.1

Vendor Advisories (1)

composerGHSA-qx76-c53f-5c7qmedium

PHP League CommonMark vulnerable to Cross-Site Scripting (XSS)

May 14, 2022

References

commonmark.thephpleague.com / changelog
Release NotesThird Party Advisory
github.com / thephpleague/commonmark/issues/337
ExploitThird Party Advisory
github.com / thephpleague/commonmark/releases/tag/0.18.1
Release NotesThird Party Advisory