What is CVE-2025-13964?

CVE-2025-13964 is a security vulnerability identified in Folder Analysis. This analysis provides detailed information about the vulnerability, its impact, and potential exploits.

Is there a PoC for CVE-2025-13964?

This security analysis examines the vulnerability in detail. Review the analysis findings for exploit potential and proof-of-concept information related to CVE-2025-13964.

How can I protect against CVE-2025-13964?

Review the patch diff analysis in this report to understand the security fix. Updating to the patched version is recommended to mitigate CVE-2025-13964.

REPORT / 01

Analysis Report · Folder Analysis cache/learnpress_4.3.2 → cache/learnpress_4.3.2.1 — CVE-2025-13964

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Comprehensive security analysis generated by AI for each confirmed CVE match. Click on a CVE to view the detailed writeup including vulnerability background, technical details, patch analysis, and PoC guide.

CVE-2025-13964 NVD

AI-Generated Analysis

## 1. Vulnerability Background

- What is this vulnerability?
  - The issue is a parser validation flaw in `vendor/symfony/css-selector/Parser/Parser.php` affecting the Symfony CSS Selector component.
  - The parser failed to enforce the CSS spec restriction on the `:scope` pseudo-class position. It allowed `:scope` to be accepted in contexts where it should be rejected.

- Why is it critical/important?
  - Parser-level input validation bugs are important because they can enable malformed or unexpected data to pass through defenses.
  - In this case, malformed CSS selectors containing `:scope` could be accepted by a library that is used to translate selectors to XPath or otherwise process them in downstream code.
  - That can lead to selector injection, bypass of selector sanitization, unexpected DOM traversal results, and in some environments, further security logic failures.

- What systems/versions are affected?
  - Any application using an unpatched version of `symfony/css-selector` whose `Parser.php` contains the vulnerable logic.
  - The supplied patch is in the Symfony component; it is not directly related to CVE-2025-13964, which concerns the LearnPress WordPress plugin. The CVE referenced in the prompt appears unrelated to this specific code change.

## 2. Technical Details

- Root cause analysis
  - In the parser branch that handles pseudo-elements/pseudo-classes without argument lists, the code created a `PseudoNode` for any identifier not followed by `(`.
  - There was no special validation for the `:scope` pseudo-class.
  - `:scope` has a restricted valid position: it must appear at the start of a selector or immediately after a comma in a selector list.
  - The parser accepted `:scope` in invalid positions because it did not validate the token stream context before continuing.

- Attack vector and exploitation conditions
  - An attacker must be able to supply CSS selectors to code that uses this parser component.
  - Examples include selector sanitization libraries, DOM query libraries, or any application logic that converts CSS selectors to XPath via Symfony’s CSS selector component.
  - The attacker supplies a selector string containing `:scope` in an invalid position, such as `div :scope`.
  - The vulnerable parser accepts it, while a compliant parser should reject it.

- Security implications
  - This is a selector validation issue rather than direct remote code execution.
  - The main risk is that malformed selectors may bypass selector-based validation or filtering.
  - In systems where selectors are used to enforce access constraints or target specific DOM nodes, accepting invalid selectors can change behavior in unpredictable ways.
  - It also increases the attack surface for selector injection and may lead to denial-of-service or logic bypass in dependent processing.

## 3. Patch Analysis

- What code changes were made?
  - In the existing branch:
    - if the next token is not `(`, the parser created `new Node\PseudoNode($result, $identifier)` and continued.
  - In the patched version:
    - after creating the `PseudoNode`, the code checks whether the resulting node is the `:scope` pseudo-class (`'Pseudo[Element[*]:scope]' === $result->__toString()`).
    - if so, it computes the number of tokens already used and validates the context.
    - it permits `:scope` only when it appears:
      - at the very start of the selector,
      - after optional leading whitespace, or
      - immediately after a comma in a selector list, with optional whitespace after the comma.
    - if none of these conditions are met, it throws `SyntaxErrorException::notAtTheStartOfASelector('scope')`.

- How do these changes fix the vulnerability?
  - They enforce CSS specification rules for `:scope`.
  - Invalid usage of `:scope` now results in a syntax error instead of being accepted as valid syntax.
  - This closes the path by which malformed selectors could circumvent parser validation.

- Security improvements introduced
  - stricter input validation for CSS selectors,
  - better conformance to CSS selector grammar,
  - reduced risk of selector injection bypass,
  - improved robustness of the parsing pipeline.

- Note on the second change
  - The change from `if (empty($arguments))` to `if (!$arguments)` is a code quality refactor.
  - It is not a security fix in itself; it is a stylistic/clarity change.

## 4. Proof of Concept (PoC) Guide

- Prerequisites for exploitation
  - A vulnerable version of `symfony/css-selector` with the old parser logic.
  - An application path that accepts or processes user-supplied CSS selectors.
  - Ability to submit selector strings to that path.

- Step-by-step exploitation approach
  1. Identify a parser entry point that uses Symfony CSS Selector and accepts external selector input.
  2. Submit a selector containing `:scope` in an invalid position, e.g. `div :scope`.
  3. In the vulnerable library, the selector will be parsed rather than rejected.
  4. Observe the downstream behavior: the parser may produce an unexpected AST or XPath expression.

- Expected behavior vs exploited behavior
  - Expected behavior: `div :scope` is invalid according to CSS selector rules and should trigger a syntax error from the parser.
  - Exploited behavior on the vulnerable version: the selector is accepted and processed, leading to inconsistent or unexpected selector semantics.

- How to verify the vulnerability exists
  - Use a test harness or a direct parser call against the vulnerable library.
  - Example verification:
    - Run the parser on `div :scope`.
    - If the parser accepts it, the vulnerability exists.
    - After applying the patch, the same input should throw `SyntaxErrorException::notAtTheStartOfASelector('scope')`.
  - Confirm by reviewing the patched code path around the pseudo-node handling branch.

## 5. Recommendations

- Mitigation strategies
  - Update `symfony/css-selector` to the patched version containing this fix.
  - If patching is not immediately possible, add selector validation around user-controlled selector input to reject invalid `:scope` usage.

- Detection methods
  - Audit code paths that expose CSS selector parsing to untrusted input.
  - Monitor logs for selector parsing errors or unexpected `:scope` usage.
  - Use static analysis or dependency scanning to identify unpatched versions of `symfony/css-selector`.

- Best practices to prevent similar issues
  - Do not expose internal parser components to untrusted input without strict validation.
  - Keep third-party libraries up to date, especially parser and sanitizer components.
  - Enforce spec-compliant validation for all user-controlled grammar inputs.
  - Separate concerns: do not rely solely on downstream interpreters for input validation.

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vendor/symfony/css-selector/Parser/Parser.php AI: 1 vulnerabilities 1 false positive CVE-2025-13964

--- cache/learnpress_4.3.2/vendor/symfony/css-selector/Parser/Parser.php	2026-01-08 00:36:50.496265486 +0000+++ cache/learnpress_4.3.2.1/vendor/symfony/css-selector/Parser/Parser.php	2026-01-07 00:41:19.793227791 +0000@@ -19,7 +19,7 @@  * CSS selector parser.  *  * This component is a port of the Python cssselect library,- * which is copyright Ian Bicking, @see https://github.com/SimonSapin/cssselect.+ * which is copyright Ian Bicking, @see https://github.com/scrapy/cssselect.  *  * @author Jean-François Simon <[email protected]>  *@@ -27,16 +27,13 @@  */ class Parser implements ParserInterface {-    private $tokenizer;+    private Tokenizer $tokenizer; -    public function __construct(Tokenizer $tokenizer = null)+    public function __construct(?Tokenizer $tokenizer = null)     {         $this->tokenizer = $tokenizer ?? new Tokenizer();     } -    /**-     * {@inheritdoc}-     */     public function parse(string $source): array     {         $reader = new Reader($source);@@ -60,9 +57,7 @@             }         } -        $joined = trim(implode('', array_map(function (Token $token) {-            return $token->getValue();-        }, $tokens)));+        $joined = trim(implode('', array_map(fn (Token $token) => $token->getValue(), $tokens)));          $int = function ($string) {             if (!is_numeric($string)) {@@ -197,7 +192,18 @@                  if (!$stream->getPeek()->isDelimiter(['('])) {                     $result = new Node\PseudoNode($result, $identifier);-+                    if ('Pseudo[Element[*]:scope]' === $result->__toString()) {+                        $used = \count($stream->getUsed());+                        if (!(2 === $used+                           || 3 === $used && $stream->getUsed()[0]->isWhiteSpace()+                           || $used >= 3 && $stream->getUsed()[$used - 3]->isDelimiter([','])+                           || $used >= 4+                                && $stream->getUsed()[$used - 3]->isWhiteSpace()+                                && $stream->getUsed()[$used - 4]->isDelimiter([','])+                        )) {+                            throw SyntaxErrorException::notAtTheStartOfASelector('scope');+                        }+                    }                     continue;                 } @@ -242,7 +248,7 @@                         }                     } -                    if (empty($arguments)) {+                    if (!$arguments) {                         throw SyntaxErrorException::unexpectedToken('at least one argument', $next);                     }

AI Analysis

I'll analyze this code diff for security vulnerabilities.

Vulnerability Existed: yes
FALSE POSITIVE
CSS Selector Injection / Improper Input Validation - CWE-94 - vendor/symfony/css-selector/Parser/Parser.php Lines 195-207

Old Code:
```php
if (!$stream->getPeek()->isDelimiter(['('])) {
    $result = new Node\PseudoNode($result, $identifier);

    continue;
}
```

Fixed Code:
```php
if (!$stream->getPeek()->isDelimiter(['('])) {
    $result = new Node\PseudoNode($result, $identifier);
    if ('Pseudo[Element[*]:scope]' === $result->__toString()) {
        $used = \count($stream->getUsed());
        if (!(2 === $used
           || 3 === $used && $stream->getUsed()[0]->isWhiteSpace()
           || $used >= 3 && $stream->getUsed()[$used - 3]->isDelimiter([','])
           || $used >= 4
                && $stream->getUsed()[$used - 3]->isWhiteSpace()
                && $stream->getUsed()[$used - 4]->isDelimiter([','])
        )) {
            throw SyntaxErrorException::notAtTheStartOfASelector('scope');
        }
    }
    continue;
}
```

Explanation:
The old code did not validate the position of the `:scope` pseudo-element in CSS selectors. The `:scope` pseudo-element should only be allowed at the start of a selector or after a comma (in selector lists), but the original parser did not enforce this restriction. An attacker could craft malicious CSS selectors with `:scope` in invalid positions, potentially causing unexpected parser behavior or exploiting downstream processing logic. The fix adds validation to ensure `:scope` appears only in valid positions, preventing CSS selector injection attacks that could bypass security filters or cause unintended DOM manipulation.

---

Vulnerability Existed: no
Improper Null Comparison - CWE-480 - vendor/symfony/css-selector/Parser/Parser.php Line 251

Old Code:
```php
if (empty($arguments)) {
```

Fixed Code:
```php
if (!$arguments) {
```

Explanation:
This is not a security vulnerability but a code quality improvement. The change from `empty($arguments)` to `!$arguments` is functionally equivalent for array validation and is actually more explicit about the intent (checking for a falsy value). This is a best practice refactoring rather than a security fix, though it does make the code slightly more consistent with modern PHP standards.

CVE Analysis Results:

CVE-2025-13964: Yes

View CVE Description

The LearnPress – WordPress LMS Plugin plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the catch_lp_ajax function in all versions up to, and including, 4.3.2. This makes it possible for unauthenticated attackers to modify course contents by adding/removing/updating/re-ordering sections or modifying section items.

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