🛡️ CVE-2021-41816 — cgi

🔴 CVSS 9.5 — Critical ✅ No Known Exploit CWE-190 OSV
9.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Buffer overrun in CGI.escape_html

A buffer overrun vulnerability was discovered in CGI.escape_html. This can lead to a buffer overflow when a user passes a very large string (> 700 MB) to CGI.escape_html on a platform where long type takes 4 bytes, typically, Windows.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2021-41816 is classified as CWE-190: Integer Overflow or Wraparound. Arithmetic produces a value too large for its type and wraps around, so a later size or bounds check passes when it should not.

Affected software

CVE-2021-41816 is recorded against 1 package.

  • cgi (fixed in 0.1.0.1)

Timeline and source

Published on 14 December 2021 and last revised on 4 February 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

nvd.nist.gov (Advisory)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
hackerone.com (Web)
www.ruby-lang.org (Web)
security.netapp.com (Web)
security.gentoo.org (Web)
security-tracker.debian.org (Web)
lists.fedoraproject.org (Web)
lists.fedoraproject.org (Web)
lists.fedoraproject.org (Web)
lists.fedoraproject.org (Web)
groups.google.com (Web)

CVE-2021-41816 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity CRITICAL
CVSS Score 9.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE CWE-190
Public Exploit ✅ No
Source OSV
Published 2021-12-14
Updated 2026-08-12
Modified 2026-02-04
Fix URL N/A

Affected Packages

Software From version Fixed in
cgi — 0.1.0.1

References

Exploit Protection

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CVE-2021-41816 carries CVSS 9.5 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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