---
id: "CVE-2026-41508"
kind: "vulnerability"
aliases: ["CVE-2026-41508", "GHSA-r3rm-qphw-hh76", "GO-2026-6670"]
title: "Coraza: Truncated multipart body bypasses MULTIPART_STRICT_ERROR (rule 200003) via silent io.ErrUnexpectedEOF handling in github.com/corazawaf/coraza"
severity: "medium"
cvss: 5.8
epss: 0.00494
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/corazawaf/coraza", "fixed": [], "affected": "all versions", "ecosystem": "go"}, {"name": "github.com/corazawaf/coraza/v2", "fixed": [], "affected": "all versions", "ecosystem": "go"}, {"name": "github.com/corazawaf/coraza/v3", "fixed": ["3.8.0"], "affected": ">= 3.4.0, < 3.8.0", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["coraza", "go", "modsecurity", "package", "waf"]
not_affected_if: ["coraza-3.8.0-or-later", "coraza-below-3.4.0", "no-multipart-body-inspection"]
published_at: "2026-10-12T21:17:17+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T19:58:08+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6670", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-41508", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41508", "first_seen_at": "2026-10-23T19:14:51+00:00"}]
---

# Coraza: Truncated multipart body bypasses MULTIPART_STRICT_ERROR (rule 200003) via silent io.ErrUnexpectedEOF handling in github.com/corazawaf/coraza

The Coraza Go WAF library, versions 3.4.0 through 3.8.0, treats a truncated multipart body as a non-fatal parse error and does not set MULTIPART_STRICT_ERROR. An attacker can send a truncated multipart body so that the strict-error rules 200002 and 200003 never fire, letting multipart parser-disagreement payloads reach a backend that reads the body differently.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- go:github.com/corazawaf/coraza affected all versions fixed ?
- go:github.com/corazawaf/coraza/v2 affected all versions fixed ?
- go:github.com/corazawaf/coraza/v3 affected >= 3.4.0, < 3.8.0 fixed 3.8.0

## How to check

go list -m github.com/corazawaf/coraza/v3
If the reported version is >= 3.4.0 and < 3.8.0, the module is affected.

## Fix

Upgrade github.com/corazawaf/coraza/v3 to 3.8.0 or later.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6670
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-41508
- 2026-10-23T19:14:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-41508

## From the sources

OWASP Coraza WAF is a golang modsecurity compatible web application firewall library. From 3.4.0 until 3.8.0, the multipart processor in internal/bodyprocessors/multipart.go treats io.ErrUnexpectedEOF as nonfatal without setting MULTIPART_STRICT_ERROR. A remote attacker can submit a truncated multipart body that produces io.ErrUnexpectedEOF, causing parsing to stop without raising the strict-error signal used by the recommended defensive rule. Rules 200002 and 200003 do not fire, allowing multipart parser-disagreement payloads to reach a backend that interprets the truncated body differently. This issue is fixed in version 3.8.0.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_