CVE-2021-47996Network attack vectorHinoki check available

Service interruption via bundled libxml2 memory flaws

Published Aug 25, 2026 · Updated Aug 28, 2026

Memory-safety flaws in bundled libxml2 in Nokogiri before 1.11.4 allow remote attackers to crash XML-processing applications. The bundled libxml2 2.9.10 leaks memory in xmlSchemaValidateStream, over-reads buffers in xmlEncodeEntitiesInternal, and contains heap-overflow and out-of-bounds-read paths for crafted XML. Exposure requires the CRuby implementation to process attacker-controlled XML while using Nokogiri's packaged libxml2; JRuby and system-library builds are outside this advisory.

CVSS severity7.5
High
EPSS probabilityUnavailable
No score available in this record
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Memory-safety flaws in bundled libxml2 in Nokogiri before 1.11.4 allow remote attackers to crash XML-processing applications. The bundled libxml2 2.9.10 leaks memory in xmlSchemaValidateStream, over-reads buffers in xmlEncodeEntitiesInternal, and contains heap-overflow and out-of-bounds-read paths for crafted XML. Exposure requires the CRuby implementation to process attacker-controlled XML while using Nokogiri's packaged libxml2; JRuby and system-library builds are outside this advisory.

The record

CVE
CVE-2021-47996
Published
Aug 25, 2026
Updated
Aug 28, 2026
Vendor
Sparkle Motion
Product
Nokogiri
Classifications
CWE-119, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.11.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Sparkle Motion · Nokogiriversion=0 <1.11.4

Published CVSS scores

7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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