CVE-2021-29059Public exploitNetwork attack vector

Process hang via backtracking SVG validation regexes

Published Jun 21, 2021 · Updated Aug 3, 2024

Regular expression denial of service in is-svg 2.1.0 through 4.2.2 allows attackers to hang a Node.js process with crafted invalid SVG input. The isSvg function applies entityRegex and removeDtdMarkupDeclarations patterns with ambiguous repetition to attacker-controlled text, causing excessive backtracking. Any application that passes an untrusted string or buffer to the library exposes its event loop to prolonged blocking; no data read or modification is reported.

CVSS severity7.5
High
EPSS probability2.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in is-svg 2.1.0 through 4.2.2 allows attackers to hang a Node.js process with crafted invalid SVG input. The isSvg function applies entityRegex and removeDtdMarkupDeclarations patterns with ambiguous repetition to attacker-controlled text, causing excessive backtracking. Any application that passes an untrusted string or buffer to the library exposes its event loop to prolonged blocking; no data read or modification is reported.

The record

CVE
CVE-2021-29059
Published
Jun 21, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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