NVD / CVE Program· CNA GitHub_M

CVE-2020-4054: Cross-site Scripting in Sanitize

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 79.8% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: rgrove Sanitize 5.2.1.

Low priority for now. Upgrade to rgrove Sanitize 5.2.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In Sanitize (RubyGem sanitize) greater than or equal to 3.0.0 and less than 5.2.1, there is a cross-site scripting vulnerability. When HTML is sanitized using Sanitize's "relaxed" config, or a custom config that allows certain elements, some content in a math or svg element may not be sanitized correctly even if math and svg are not in the allowlist. You are likely to be vulnerable to this issue if you use Sanitize's relaxed config or a custom config that allows one or more of the following HTML elements: iframe, math, noembed, noframes, noscript, plaintext, script, style, svg, xmp. Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser. This has been fixed in 5.2.1.

HighCVSS 7.3 · v3.1—No exploit Fix available

Published: Jun 16, 2020
Updated: Jun 16, 2026
EPSS: 1.9% · 79th percentile
CWE: CWE-79

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 29 / 40 · 7.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 1.9%

CNA vs NVD score

NVD: 7.3
CNA · GitHub_M: 7.3; agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
sanitize project	sanitize	cpe:2.3:a:sanitize_project:sanitize

Limit the impact of XSS

This is a cross-site scripting (XSS) vulnerability. A well-configured Content-Security-Policy doesn't fix it, but greatly reduces its impact. Check your site's CSP and other security headers for free.

Check security headers

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

sanitize project sanitize3.0.0 and later · before 5.2.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

rgrove Sanitize
- >= 3.0.0, < 5.2.1affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:10	ruby-sanitize	before 4.6.6-2.1~deb10u1	4.6.6-2.1~deb10u1
Debian:12	ruby-sanitize	before 4.6.6-2.1	4.6.6-2.1
RubyGems	sanitize	from 3.0.0 · before 5.2.1	5.2.1

Same product

sanitize project: all records

Other highest-scoring records for the same primary product.

CVE-2018-3740A specially crafted HTML fragment can cause Sanitize gem for Ruby to allow non-whitelisted attributes to be used on a whitelisted HTML eleme
30Monitor
CVE-2023-36823Sanitize vulnerable to Cross-site Scripting via insufficient neutralization of `style` element content
24Monitor
CVE-2023-23627Sanitize vulnerable to Cross-site Scripting via Improper neutralization of `noscript` element
24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
rgrove Sanitize	5.2.1 · description	Vendor (CNA)
debian:ruby-sanitize	4.6.6-2.1 · Debian:12	Package registry (OSV)
RubyGems:sanitize	5.2.1	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

rgrove/sanitizecommit a11498d

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: low · data can be read
Integrity: low · data or configuration can be modified
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: Low
Integrity impact: Low
Availability impact: Low

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

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

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1commentEl.innerHTML = comment.body;

Fixed

1commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

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References

www.debian.org/security/2020/dsa-4730

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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