Vulnerability · Published Jul 10, 2026 · Assigned by GitHub_M
CVE-2026-52747ModSecurity: Multipart form-data parser silently strips embedded line breaks from form-field values, enabling request-body inspection bypass
High 8.6
In plain English
A high-severity security flaw in ModSecurity from owasp-modsecurity. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 3.0.16, the multipart/form-data request body parser in libmodsecurity silently removes embedded line breaks from non-file form-field values before exporting them to ARGS and ARGS_POST because src/request_body_processor/multipart.cc overwrites reserved bytes in m_reserve instead of appending the current buffer. This creates a parser differential between ModSecurity and backend applications that preserve line breaks in form fields, allowing rules that inspect ARGS or ARGS_POST to miss payloads whose dangerous syntax depends on a line break. This issue is fixed in version 3.0.16.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | modsecurity | no fix listed | DEBIAN-CVE-2026-52747 |
| Debian:13 | modsecurity | no fix listed | DEBIAN-CVE-2026-52747 |
| Debian:14 | modsecurity | 3.0.16-1 | DEBIAN-CVE-2026-52747 |
| Ubuntu:22.04:LTS | modsecurity | no fix listed | UBUNTU-CVE-2026-52747 |
| Ubuntu:24.04:LTS | modsecurity | no fix listed | UBUNTU-CVE-2026-52747 |
| Ubuntu:26.04:LTS | modsecurity | no fix listed | UBUNTU-CVE-2026-52747 |
| Ubuntu:26.10 | modsecurity | no fix listed | UBUNTU-CVE-2026-52747 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| owasp-modsecurity | ModSecurity | < 3.0.16 |
Weakness: CWE-180 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
References
- https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-rcw9-2f5r-7p88 x_refsource_CONFIRM
- https://github.com/owasp-modsecurity/ModSecurity/commit/875504c2758169c41be1ad2f0cc64d896b7815d7 x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.16 x_refsource_MISC