CVE-2026-42551

Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin. This vulnerability is fixed in 3.18.1.

Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin. This vulnerability is fixed in 3.18.1.

Summary

Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin.

Affected code

flight/net/Request.php (≈ lines 281-292):

public static function getMethod(): string
{
    $method = self::getVar('REQUEST_METHOD', 'GET');
    if (self::getVar('HTTP_X_HTTP_METHOD_OVERRIDE') !== '') {
        $method = self::getVar('HTTP_X_HTTP_METHOD_OVERRIDE');
    } elseif (isset($_REQUEST['_method']) === true) {
        $method = $_REQUEST['_method'];
    }
    return strtoupper($method);
}

$_REQUEST aggregates $_GET and $_POST; on PHP runtimes with request_order=GPC it also includes $_COOKIE.

Proof of concept

GET /item/42?_method=DELETE        HTTP/1.1

is dispatched as DELETE /item/42.

GET /item/42                       HTTP/1.1
X-HTTP-Method-Override: DELETE

is also dispatched as DELETE /item/42.

Trivial CSRF vector (no JavaScript required):

<img src="https://victim.tld/item/42?_method=DELETE">

loaded on any attacker-controlled page triggers the destructive DELETE on page load, bypassing Same-Origin Policy (image loads are not blocked).

Reproduced against /poc4/item/42.

Impact

• GET → DELETE / PUT CSRF on any route registered for unsafe verbs.
• Bypass of authentication, CSRF token, or rate-limiting middleware that is gated only on POST/DELETE.
• CDN cache poisoning: the CDN caches the GET response body while the origin executed a DELETE.

Patch (fixed in 3.18.1, commit b8dd23a)

A new flight.allow_method_override setting controls both override vectors. Operators can set it to false to disable X-HTTP-Method-Override and _method entirely.

Credit

Discovered by @Rootingg.

Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin. This vulnerability is fixed in 3.18.1.

Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin. This vulnerability is fixed in 3.18.1.

Summary

Request::getMethod() unconditionally honors the X-HTTP-Method-Override header and the $_REQUEST['_method'] parameter on any HTTP verb (including safe verbs such as GET), with no opt-in and no whitelist of permitted target methods. A GET request can silently become a DELETE or PUT, enabling CSRF escalation against destructive endpoints, bypass of middleware gated on unsafe verbs, and cache poisoning between CDN and origin.

Affected code

flight/net/Request.php (≈ lines 281-292):

public static function getMethod(): string
{
    $method = self::getVar('REQUEST_METHOD', 'GET');
    if (self::getVar('HTTP_X_HTTP_METHOD_OVERRIDE') !== '') {
        $method = self::getVar('HTTP_X_HTTP_METHOD_OVERRIDE');
    } elseif (isset($_REQUEST['_method']) === true) {
        $method = $_REQUEST['_method'];
    }
    return strtoupper($method);
}

$_REQUEST aggregates $_GET and $_POST; on PHP runtimes with request_order=GPC it also includes $_COOKIE.

Proof of concept

GET /item/42?_method=DELETE        HTTP/1.1

is dispatched as DELETE /item/42.

GET /item/42                       HTTP/1.1
X-HTTP-Method-Override: DELETE

is also dispatched as DELETE /item/42.

Trivial CSRF vector (no JavaScript required):

<img src="https://victim.tld/item/42?_method=DELETE">

loaded on any attacker-controlled page triggers the destructive DELETE on page load, bypassing Same-Origin Policy (image loads are not blocked).

Reproduced against /poc4/item/42.

Impact

• GET → DELETE / PUT CSRF on any route registered for unsafe verbs.
• Bypass of authentication, CSRF token, or rate-limiting middleware that is gated only on POST/DELETE.
• CDN cache poisoning: the CDN caches the GET response body while the origin executed a DELETE.

Patch (fixed in 3.18.1, commit b8dd23a)

A new flight.allow_method_override setting controls both override vectors. Operators can set it to false to disable X-HTTP-Method-Override and _method entirely.

Credit

Discovered by @Rootingg.