CVE-2026-33691
OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
6.8
OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks
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.
- Record
CVE-2026-33691- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N - Weakness
- CWE-178
- Updated
- 2026-11-02
EUVDEUVD-2026-18352
6.8
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.
- Record
EUVD-2026-18352- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N - Updated
- 2026-11-02
NVD
6.8
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.
- Record
CVE-2026-33691- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-178
- Updated
- 2026-11-02
OSV
6.8
OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks
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.
- Record
CVE-2026-33691- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N - Weakness
- CWE-178
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-33691
7.5
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.
- Record
DEBIAN-CVE-2026-33691- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-33691
6.8
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.
- Record
UBUNTU-CVE-2026-33691- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:11632-1 No score
owasp-modsecurity-crs-4.29.0-1.1 on GA media
These are all security issues fixed in the owasp-modsecurity-crs-4.29.0-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:11632-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
modsecurity-crsDebian:12 |
before 3.3.4-1+deb12u3, plus listed versions 3.3.4-13.3.4-1+deb12u13.3.4-1+deb12u2 |
3.3.4-1+deb12u3 |
modsecurity-crsDebian:13 |
before 3.3.7-1+deb13u2, plus listed versions 3.3.7-13.3.7-1+deb13u1 |
3.3.7-1+deb13u2 |
modsecurity-crsDebian:14 |
before 3.3.9-1, plus listed versions 3.3.7-13.3.8-1 |
3.3.9-1 |
modsecurity-crsUbuntu:16.04:LTS |
All versions, plus listed versions 2.2.9-1 |
None known |
modsecurity-crsUbuntu:18.04:LTS |
All versions, plus listed versions 3.0.0-33.0.2-1 |
None known |
modsecurity-crsUbuntu:20.04:LTS |
All versions, plus listed versions 3.1.1-13.2.0-1 |
None known |
modsecurity-crsUbuntu:22.04:LTS |
All versions, plus listed versions 3.3.0-13.3.2-1 |
None known |
modsecurity-crsUbuntu:24.04:LTS |
All versions, plus listed versions 3.3.5-13.3.5-2 |
None known |
modsecurity-crsUbuntu:25.10 |
All versions, plus listed versions 3.3.7-1 |
None known |
modsecurity-crsUbuntu:26.10 |
All versions, plus listed versions 3.3.8-13.3.9-1 |
None known |
modsecurity-crsUbuntu:26.04:LTS |
All versions, plus listed versions 3.3.7-13.3.8-1 |
None known |
owasp-modsecurity-crsopenSUSE:Tumbleweed |
before 4.29.0-1.1 | 4.29.0-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-33691 is a medium vulnerability (CVSS 6.8) in Coreruleset, published April 2, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.84%, the 90th percentile. Fixed in modsecurity-crs 3.3.4-1+deb12u3.
References
github.com/coreruleset/coreruleset/security/advisories/GHSA-rw5f-9w43-gv2w
github.com/coreruleset/coreruleset/pull/4546
github.com/coreruleset/coreruleset/pull/4547
github.com/coreruleset/coreruleset/pull/4548
github.com/coreruleset/coreruleset/commit/2a8c63512811c5dd74472becebb79a783e68ff02
github.com/coreruleset/coreruleset/releases/tag/v3.3.9
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github.com/coreruleset/coreruleset/releases/tag/v4.25.0
openwall.com/lists/oss-security/2026/03/29/2
seclists.org/fulldisclosure/2026/Apr/0
openwall.com/lists/oss-security/2026/04/18/4
github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33691.json
nvd.nist.gov/vuln/detail/CVE-2026-33691
security-tracker.debian.org/tracker/CVE-2026-33691
ubuntu.com/security/CVE-2026-33691
cve.org/CVERecord?id=CVE-2026-33691
suse.com/security/cve/CVE-2026-33691