CVE-2021-41816Network attack vector

Application interruption via escaped-length integer overflow

Published Feb 6, 2022 · Updated Aug 4, 2024

Buffer overflow in Ruby 2.7 before 2.7.5, Ruby 3.0 before 3.0.3, and CGI gem before 0.3.1 allows attackers to interrupt applications. CGI.escape_html calculates the escaped length of a string larger than 700 MB using a narrower long than size_t, causing the allocation calculation to wrap before data is copied into the buffer. Exploitation requires a reachable application path on a platform with different long and size_t widths, typically Windows; arbitrary code execution is not established.

CVSS severity9.8
Critical
EPSS probability4.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in Ruby 2.7 before 2.7.5, Ruby 3.0 before 3.0.3, and CGI gem before 0.3.1 allows attackers to interrupt applications. CGI.escape_html calculates the escaped length of a string larger than 700 MB using a narrower long than size_t, causing the allocation calculation to wrap before data is copied into the buffer. Exploitation requires a reachable application path on a platform with different long and size_t widths, typically Windows; arbitrary code execution is not established.

The record

CVE
CVE-2021-41816
Published
Feb 6, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P
7.5Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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