CVE-2026-104269: ModSecurity: RFC 2231 `filename*` Parameter Bypasses Multipart Filename Rules on RFC-Compliant Backends (Go, Python, Node, Java)
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-08 00:03 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 until 3.0.17, ModSecurity’s multipart parser does not apply the RFC 2231 filename* parameter precedence used by common Go, Python, Node.js, and Java application parsers. A Content-Disposition header can provide a benign filename parameter for ModSecurity and a different encoded filename* value that the backend prefers, causing MULTIPART_FILENAME rules and the application to make security decisions on different names. Applications that use the backend-selected name for storage, extension checks, or content-type inference can therefore receive a filename that bypassed WAF inspection. PHP’s native multipart parser is not affected by this discrepancy. This issue is fixed in version 3.0.17.
Description quoted from the CVE record (assigned by GitHub_M, published 2026-11-05).
Weakness: CWE-436: Interpretation Conflict
How it can be exploited
Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality none, integrity high, availability none. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: yes. Technical impact: partial.
Public exploit evidence (Exploit Observer)
Exploit Observer has no public exploit code naming this CVE. Check Exploit Observer for anything new.
Live scores
- EPSS
- 0.006
low predicted chance of attack - VEDAS
- 0.096
little exploit evidence - On CISA KEV
- Not listed
- Detection rule
- No public rule yet
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| owasp-modsecurity ModSecurity | version >= 3.0.0, < 3.0.17 | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.
How to detect it
There is no open VEDAS detection rule for this bug yet. It is listed on the detection gaps page if CISA has confirmed attacks.
Advisories on this CVE
- GBHackers reports ModSecurity WAF upload bypass and XML flaw (full advisory)
References
Other references
- https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-5pww-8rfg-9crf (x_refsource_CONFIRM)
- https://github.com/owasp-modsecurity/ModSecurity/commit/463db0c840fa27bfba095b0406a63004a12884b0 (x_refsource_MISC)
- https://github.com/owasp-modsecurity/ModSecurity/commit/c6bd53d2dd96766b3afdc35d9929ebb20925d13d (x_refsource_MISC)
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v2.9.15 (x_refsource_MISC)
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.17 (x_refsource_MISC)
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.
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