{
    "data_version": "4.0",
    "data_type": "CVE",
    "data_format": "MITRE",
    "CVE_data_meta": {
        "ID": "CVE-2023-40021",
        "ASSIGNER": "security-advisories@github.com",
        "STATE": "PUBLIC"
    },
    "description": {
        "description_data": [
            {
                "lang": "eng",
                "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."
            }
        ]
    },
    "problemtype": {
        "problemtype_data": [
            {
                "description": [
                    {
                        "lang": "eng",
                        "value": "CWE-203: Observable Discrepancy",
                        "cweId": "CWE-203"
                    }
                ]
            },
            {
                "description": [
                    {
                        "lang": "eng",
                        "value": "CWE-208: Observable Timing Discrepancy",
                        "cweId": "CWE-208"
                    }
                ]
            }
        ]
    },
    "affects": {
        "vendor": {
            "vendor_data": [
                {
                    "vendor_name": "oppia",
                    "product": {
                        "product_data": [
                            {
                                "product_name": "oppia",
                                "version": {
                                    "version_data": [
                                        {
                                            "version_affected": "=",
                                            "version_value": ">= 1.1.0, < 3.3.2-hotfix-2"
                                        }
                                    ]
                                }
                            }
                        ]
                    }
                }
            ]
        }
    },
    "references": {
        "reference_data": [
            {
                "url": "https://github.com/oppia/oppia/security/advisories/GHSA-49jp-pjc3-2532",
                "refsource": "MISC",
                "name": "https://github.com/oppia/oppia/security/advisories/GHSA-49jp-pjc3-2532"
            },
            {
                "url": "https://github.com/oppia/oppia/pull/18769",
                "refsource": "MISC",
                "name": "https://github.com/oppia/oppia/pull/18769"
            },
            {
                "url": "https://github.com/oppia/oppia/commit/b89bf808378c1236874b5797a7bda32c77b4af23",
                "refsource": "MISC",
                "name": "https://github.com/oppia/oppia/commit/b89bf808378c1236874b5797a7bda32c77b4af23"
            },
            {
                "url": "https://github.com/oppia/oppia/blob/3a05c3558a292f3db9e658e60e708c266c003fd0/core/controllers/base.py#L964-L990",
                "refsource": "MISC",
                "name": "https://github.com/oppia/oppia/blob/3a05c3558a292f3db9e658e60e708c266c003fd0/core/controllers/base.py#L964-L990"
            }
        ]
    },
    "source": {
        "advisory": "GHSA-49jp-pjc3-2532",
        "discovery": "UNKNOWN"
    },
    "impact": {
        "cvss": [
            {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N",
                "version": "3.1"
            }
        ]
    }
}