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Fencer Intel
high 8.6

CVE-2026-52747 json

ModSecurity: Multipart form-data parser silently strips embedded line breaks from form-field values, enabling request-body inspection bypass

published 4mo ago modified 17d ago also BIT-modsecurity-2026-52747 , BIT-modsecurity2-2026-52747 , EUVD-2026-43047 , GHSA-rcw9-2f5r-7p88

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami modsecurity 3.0.16
  • owasp libmodsecurity 3.0.16
  • owasp modsecurity 3.0.16
  • owasp owasp_modsecurity 3.0.16
  • trustwave modsecurity 3.0.16
  • modsecurity Debian 14 3.0.16-1

debian advisories DEBIAN-CVE-2026-52747

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-52747 updated cvss 5.8

ModSecurity: ModSecurity: Security rule bypass due to incorrect handling of line breaks in form data

  • Red Hat Enterprise Linux 7 mod_security, mod_security-mlogc
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 mod_security, mod_security-mlogc Red Hat Enterprise Linux 9 mod_security, mod_security-mlogc
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
3mo ago

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-rcw9-2f5r-7p88 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
NVD 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
OSV 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
bitnami modsecurity
<3.0.16
3.0.16

Affected products

  • owasp-modsecurity ModSecurity

Classification

Weakness
  • CWE-180 Incorrect Behavior Order: Validate Before Canonicalize

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.