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Vulnerability · Published Nov 5, 2026 · Assigned by GitHub_M

CVE-2026-73856ModSecurity: Response Body Inspection Bypass

High 8.6

In plain English

A high-severity security flaw in ModSecurity from owasp-modsecurity. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities).

Severity (CVSS 3.1)8.6High
Exploit odds (30 days)0.6%top 52.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 until 3.0.17, src/transaction.cc compares a response Content-Type value against SecResponseBodyMimeType entries case-sensitively. A mixed-case response media type that is semantically equivalent to a configured lowercase type can therefore be treated as unconfigured, causing ModSecurity to skip RESPONSE_BODY inspection. An unauthenticated requester can then receive response content that a phase 4 rule would otherwise block, including sensitive error or debug data. This issue is fixed in version 3.0.17.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12modsecurityno fix listedDEBIAN-CVE-2026-73856
Debian:13modsecurityno fix listedDEBIAN-CVE-2026-73856
Debian:14modsecurityno fix listedDEBIAN-CVE-2026-73856
Ubuntu:22.04:LTSmodsecurityno fix listedUBUNTU-CVE-2026-73856
Ubuntu:24.04:LTSmodsecurityno fix listedUBUNTU-CVE-2026-73856
Ubuntu:26.04:LTSmodsecurityno fix listedUBUNTU-CVE-2026-73856
Ubuntu:26.10modsecurityno fix listedUBUNTU-CVE-2026-73856

Affected products (as reported)

VendorProductVersions
owasp-modsecurity ModSecurity >= 3.0.0, < 3.0.17

Weakness: CWE-178 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

References