OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks (coreruleset coreruleset)
At a glance
- Source
- NVD
- EPSS
- EPSS 3.84 % · percentile 90 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Modified
Description
The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 3.3.9 and 4.25.0, a bypass was identified in OWASP CRS that allows uploading files with dangerous extensions (.php, .phar, .jsp, .jspx) by inserting whitespace padding in the filename (e.g. photo. php or shell.jsp ). The affected rules do not normalize whitespace before evaluating the file extension regex, so the dot-extension check fails to match. This issue has been patched in versions 3.3.9 and 4.25.0.
Weaknesses (CWE)
- CWE-178 — Improper Handling of Case Sensitivity
References
- https://github.com/coreruleset/coreruleset/security/advisories/GHSA-rw5f-9w43-gv2w
- https://github.com/coreruleset/coreruleset/pull/4546
- https://github.com/coreruleset/coreruleset/pull/4547
- https://github.com/coreruleset/coreruleset/pull/4548
- https://github.com/coreruleset/coreruleset/commit/2a8c63512811c5dd74472becebb79a783e68ff02
- https://github.com/coreruleset/coreruleset/releases/tag/v3.3.9
- https://github.com/coreruleset/coreruleset/releases/tag/v4.25.0
- http://www.openwall.com/lists/oss-security/2026/03/29/2
- http://seclists.org/fulldisclosure/2026/Apr/0
- http://www.openwall.com/lists/oss-security/2026/04/18/4
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 6.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N | GitHub_M |
| CVSS 3.1 | MEDIUM 6.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | NVD · nvd@nist.gov (Primary) |
European references
- ENISA EUVD · EUVD-2026-18352
- GCVE · GCVE-0-2026-33691
CERT-FR advisories
- CERTFR-2026-AVI-0883 — Multiples vulnérabilités dans Progress LoadMaster · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set:*:*:*:*:*:*:*:*< 3.3.9cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set:*:*:*:*:*:*:*:*≥ 4.0.0 < 4.25.0
Affected products
| Product | Versions |
|---|---|
| coreruleset · coreruleset | affected < 3.3.9 ; affected >= 4.0.0-rc1, < 4.25.0 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |