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Fencer Intel
medium 5.8

CVE-2026-52761 json

ModSecurity: Transformation utf8toUnicode produces wrong output on i386 architecture

published 4mo ago modified 17d ago also BIT-modsecurity-2026-52761 , BIT-modsecurity2-2026-52761 , EUVD-2026-43113 , GHSA-qjgm-7gp4-f8qq

cvss
5.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 through 3.0.15, the t:utf8toUnicode transformation in src/actions/transformations/utf8_to_unicode.cc produces wrong output on i386 architecture because snprintf uses sizeof on a char pointer rather than the length of the unicode buffer, allowing rules that use this transformation to be bypassed on i386 architecture. This issue is fixed in version 3.0.16.

Patch / fix

  • bitnami modsecurity 3.0.16
  • bitnami modsecurity2 3.0.16
  • owasp modsecurity 3.0.16
  • trustwave modsecurity 3.0.16
  • modsecurity Debian 14 3.0.16-1

debian advisories DEBIAN-CVE-2026-52761

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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-2026-52761 updated cvss 5.8

ModSecurity: ModSecurity: Web Application Firewall rules bypass due to incorrect UTF-8 to Unicode transformation

  • 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
none
Automatable
yes
Technical impact
partial
Assessed
3mo ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 5.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
bitnami modsecurity
>=3.0.0, <3.0.16
3.0.16
bitnami modsecurity2
>=3.0.0, <3.0.16
3.0.16

Affected products

  • owasp-modsecurity ModSecurity

Classification

Weakness
  • CWE-467 Use of sizeof() on a Pointer Type

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.