CVE-2026-52761Network attack vector

WAF rule bypass via truncated Unicode transformation

Published Jul 10, 2026 · Updated Jul 10, 2026

Rule bypass in OWASP ModSecurity 3.0.0 through 3.0.15 allows remote attackers to evade WAF inspection via crafted UTF-8 input. In src/actions/transformations/utf8_to_unicode.cc, snprintf receives the size of a char pointer instead of the Unicode buffer length, truncating transformed output on i386. Only i386 deployments whose rules use t:utf8toUnicode are exposed; affected rules can miss malicious request content while other architectures are unaffected.

CVSS severity5.8
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Rule bypass in OWASP ModSecurity 3.0.0 through 3.0.15 allows remote attackers to evade WAF inspection via crafted UTF-8 input. In src/actions/transformations/utf8_to_unicode.cc, snprintf receives the size of a char pointer instead of the Unicode buffer length, truncating transformed output on i386. Only i386 deployments whose rules use t:utf8toUnicode are exposed; affected rules can miss malicious request content while other architectures are unaffected.

The record

CVE
CVE-2026-52761
Published
Jul 10, 2026
Updated
Jul 10, 2026
Vendor
OWASP ModSecurity
Product
ModSecurity
Classifications
CWE-467, T1562.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 10, 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=>= 3.0.0, < 3.0.16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OWASP ModSecurity · ModSecurityversion=>= 3.0.0, < 3.0.16

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.8GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A: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-467Use of sizeof() on a Pointer Type
T1562.001Impair Defenses: Disable or Modify Tools

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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