HOMEVULNERABILITIESCVE-2021-41816
CRITICAL

CVE-2021-41816

CWE-190Published: February 6, 2022· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

CGI.escape_html in Ruby before 2.7.5 and 3.x before 3.0.3 has an integer overflow and resultant buffer overflow via a long string on platforms (such as Windows) where size_t and long have different numbers of bytes. This also affects the CGI gem before 0.3.1 for Ruby.

NVD Source

Technical Analysis

CVE-2021-41816 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Fedora1 product(s)
fedora
ruby-lang2 product(s)
cgiruby
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://hackerone.com/reports/1328463
ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2021-41816
ADVISORYhttps://security.netapp.com/advisory/ntap-20220303-0006/
ADVISORYhttps://www.ruby-lang.org/en/news/2021/11/24/buffer-overrun-in-cgi-escape_html-cve-2021-41816/
ADVISORYhttps://hackerone.com/reports/1328463
ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2021-41816
ADVISORYhttps://security.netapp.com/advisory/ntap-20220303-0006/
ADVISORYhttps://www.ruby-lang.org/en/news/2021/11/24/buffer-overrun-in-cgi-escape_html-cve-2021-41816/

All References (14)

→
https://hackerone.com/reports/1328463Permissions Required · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IUXQCH6FRKANCVZO2Q7D2SQX33FP3KWN/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UTOJGS5IEFDK3UOO7IY4OTTFGHGLSWZF/
→
https://security-tracker.debian.org/tracker/CVE-2021-41816Third Party Advisory
→
https://security.gentoo.org/glsa/202401-27
→
https://security.netapp.com/advisory/ntap-20220303-0006/Third Party Advisory
→
https://www.ruby-lang.org/en/news/2021/11/24/buffer-overrun-in-cgi-escape_html-cve-2021-41816/Exploit · Vendor Advisory
→
https://hackerone.com/reports/1328463Permissions Required · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IUXQCH6FRKANCVZO2Q7D2SQX33FP3KWN/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UTOJGS5IEFDK3UOO7IY4OTTFGHGLSWZF/
→
https://security-tracker.debian.org/tracker/CVE-2021-41816Third Party Advisory
→
https://security.gentoo.org/glsa/202401-27
→
https://security.netapp.com/advisory/ntap-20220303-0006/Third Party Advisory
→
https://www.ruby-lang.org/en/news/2021/11/24/buffer-overrun-in-cgi-escape_html-cve-2021-41816/Exploit · Vendor Advisory

Quick Facts

CVE IDCVE-2021-41816
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-190
CISA KEVNo
Affected2 vendor(s)
PublishedFeb 6, 2022

Related CVEs (CWE-190)

CVE-2025-64721
10.0
CVE-2012-5143
10.0
CVE-2015-5097
10.0
CVE-2010-1233
10.0
CVE-2012-5835
10.0
CVE-2013-2555
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-41816 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
← All Vulnerabilities·Search for CVE-2021-41816·NVD