CVE-2026-30923Public exploitNetwork attack vector

Service interruption via hexDecode loop-bound underflow

Published May 5, 2026 · Updated May 5, 2026

Stack buffer overflow in OWASP ModSecurity before 3.0.15 allows remote attackers to crash web-server worker processes via crafted requests. The libmodsecurity3 t:hexDecode transformation uses a signed integer underflow as a loop bound when decoding a one-character query value, causing an out-of-bounds stack write and segmentation fault. Exposure requires a rule that applies t:hexDecode to attacker-controlled query parameters; repeated requests exhaust workers, but service recovers after the traffic stops.

CVSS severity8.2
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in OWASP ModSecurity before 3.0.15 allows remote attackers to crash web-server worker processes via crafted requests. The libmodsecurity3 t:hexDecode transformation uses a signed integer underflow as a loop bound when decoding a one-character query value, causing an out-of-bounds stack write and segmentation fault. Exposure requires a rule that applies t:hexDecode to attacker-controlled query parameters; repeated requests exhaust workers, but service recovers after the traffic stops.

The record

CVE
CVE-2026-30923
Published
May 5, 2026
Updated
May 5, 2026
Vendor
OWASP ModSecurity
Product
ModSecurity
Classifications
CWE-190, CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 5, 2026CVE publishedPublication date reported by the CVE source.
  2. May 5, 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=< 3.0.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OWASP ModSecurity · ModSecurityversion=< 3.0.15

Published CVSS scores

8.2GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
CWE-125Out-of-bounds Read
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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