Coraza: Multipart filename* (RFC 5987) charset restriction lets a decoy filename bypass FILES-based rules

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.0 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

EPSS

• CVE-2026-114101: 0.25% estimated exploitation activity in the next 30 days; percentile 16.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Coraza extracts a multipart file upload's filename using Go's standard-library mime.ParseMediaType, which only decodes the RFC 5987/6266 extended filename Content-Disposition parameter when its declared charset is exactly us-ascii or utf-8. Any other charset — including iso-8859-1, which RFC 5987 explicitly permits — is silently dropped by the stdlib, with no error and no fallback signal. This lets an attacker present one filename to Coraza and a different one to the backend application in the same request. Affected variables FILES (documented as "the original filenames as submitted by the client in the multipart upload"), FILESSIZES, and the file-vs-field routing decision that determines whether a part is tracked as a file at all. MULTIPARTFILENAME is not affected. It is declared in Coraza but is not populated by any code path in the affected versions. Details internal/bodyprocessors/multipart.go's originFileName calls mime.ParseMediaType on the raw Content-Disposition…

Published by the source

8 Oct 2026, 17:51 UTC

Last modified by the source

21 Oct 2026, 10:57 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3wr7-993q-jrff

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6691

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3wr7-993q-jrff

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# Patch Next advisory brief: CVE-2026-114101

Advisory: Coraza: Multipart filename* (RFC 5987) charset restriction lets a decoy filename bypass FILES-based rules
IDs: CVE-2026-114101, GHSA-3wr7-993q-jrff
Record: https://patchnext.com/advisories/cve-2026-114101 (revision 3, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/corazawaf/coraza/v3 3.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/corazawaf/coraza/v3: affected < 3.8.1; fixed in 3.8.1
- Go github.com/corazawaf/coraza: affected every version
- Go github.com/corazawaf/coraza/v2: affected every version

## Suggested inspection (read-only)
- Go github.com/corazawaf/coraza/v3: check the installed version with your package manager.
- Go github.com/corazawaf/coraza: check the installed version with your package manager.
- Go github.com/corazawaf/coraza/v2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/corazawaf/coraza/v3, github.com/corazawaf/coraza, github.com/corazawaf/coraza/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6691 (OSV record GO-2026-6691 lists affected ranges: Go github.com/corazawaf/coraza >=0; Go github.com/corazawaf/coraza/v2 >=0; Go github.com/corazawaf/coraza/v3 >=0 <3.8.1 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-3wr7-993q-jrff (OSV record GHSA-3wr7-993q-jrff lists affected ranges: Go github.com/corazawaf/coraza/v3 >=0 <3.8.1 (fixed))
- Verified: https://github.com/advisories/GHSA-3wr7-993q-jrff (GitHub-reviewed advisory GHSA-3wr7-993q-jrff lists affected ranges: Go github.com/corazawaf/coraza/v3 >=0 <3.8.1)

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