{
  "id": "CVE-2023-40021",
  "sourceIdentifier": "security-advisories@github.com",
  "published": "2023-08-16T21:15:09.880",
  "lastModified": "2024-11-21T08:18:31.750",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Oppia is an online learning platform. When comparing a received CSRF token against the expected token, Oppia uses the string equality operator (`==`), which is not safe against timing attacks. By repeatedly submitting invalid tokens, an attacker can brute-force the expected CSRF token character by character. Once they have recovered the token, they can then submit a forged request on behalf of a logged-in user and execute privileged actions on that user's behalf. In particular the function to validate received CSRF tokens is at `oppia.core.controllers.base.CsrfTokenManager.is_csrf_token_valid`. An attacker who can lure a logged-in Oppia user to a malicious website can perform any change on Oppia that the user is authorized to do, including changing profile information; creating, deleting, and changing explorations; etc. Note that the attacker cannot change a user's login credentials. An attack would need to complete within 1 second because every second, the time used in computing the token changes. This issue has been addressed in commit `b89bf80837` which has been included in release `3.3.2-hotfix-2`. Users are advised to upgrade. There are no known workarounds for this vulnerability."
    }
  ],
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        "type": "Secondary",
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          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "REQUIRED",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 1.6,
        "impactScore": 3.6
      },
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        "type": "Primary",
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          "privilegesRequired": "NONE",
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          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
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          "availabilityImpact": "NONE"
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        "impactScore": 3.6
      }
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  "weaknesses": [
    {
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      "description": [
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          "value": "CWE-203"
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      "nodes": [
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          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:oppia:oppia:*:*:*:*:*:*:*:*",
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  "references": [
    {
      "url": "https://github.com/oppia/oppia/blob/3a05c3558a292f3db9e658e60e708c266c003fd0/core/controllers/base.py#L964-L990",
      "source": "security-advisories@github.com",
      "tags": [
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    {
      "url": "https://github.com/oppia/oppia/commit/b89bf808378c1236874b5797a7bda32c77b4af23",
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