CVE-2026-28388

# This is a conceptual PoC to demonstrate the creation of a malformed Delta CRL. # In a real scenario, this would require crafting specific ASN.1 structures. import sys def create_malformed_delta_crl(): """ Simulates the creation of a CRL with Delta CRL Indicator extension but missing the CRL Number extension. """ # Note: Actual exploitation requires constructing a valid ASN.1 CRL structure # with specific extensions present and absent. # This script represents the logic flow. print("[*] Generating malformed Delta CRL structure...") # 1. Create a base CRL structure (simplified) crl_data = {} # 2. Add Delta CRL Indicator extension (Required for the vulnerability path) crl_data['extensions'] = { 'DeltaCRLIndicator': True, # This extension is present 'CRLNumber': None # This extension is MISSING (NULL) } # 3. Serialize and send to target malicious_payload = crl_data return malicious_payload if __name__ == "__main__": payload = create_malformed_delta_crl() print(f"[!] Malformed payload prepared: {payload}") print("[!] Send this to an application processing CRLs with X509_V_FLAG_USE_DELTAS enabled.")

{"cve": {"id": "CVE-2026-28388", "sourceIdentifier": "[email protected]", "published": "2026-04-07T22:16:20.863", "lastModified": "2026-05-12T13:17:33.453", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Issue summary: When a delta CRL that contains a Delta CRL Indicator extension\nis processed a NULL pointer dereference might happen if the required CRL\nNumber extension is missing.\n\nImpact summary: A NULL pointer dereference can trigger a crash which\nleads to a Denial of Service for an application.\n\nWhen CRL processing and delta CRL processing is enabled during X.509\ncertificate verification, the delta CRL processing does not check\nwhether the CRL Number extension is NULL before dereferencing it.\nWhen a malformed delta CRL file is being processed, this parameter\ncan be NULL, causing a NULL pointer dereference.\n\nExploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in\nthe verification context, the certificate being verified to contain a\nfreshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and\nan attacker to provide a malformed CRL to an application that processes it.\n\nThe vulnerability is limited to Denial of Service and cannot be escalated to\nachieve code execution or memory disclosure. For that reason the issue was\nassessed as Low severity according to our Security Policy.\n\nThe FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue,\nas the affected code is outside the OpenSSL FIPS module boundary."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.0.2", "versionEndExcluding": "1.0.2zp", "matchCriteriaId": "CE7957CC-80F0-4907-BFB5-AFB6994DDE3C"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.1.1", "versionEndExcluding": "1.1.1zg", "matchCriteriaId": "656A0540-5825-498E-A7AB-C14976FEE45D"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.0", "versionEndExcluding": "3.0.20", "matchCriteriaId": "B28A8143-89A4-4332-A1F8-A65FB5AA829F"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.3.0", "versionEndExcluding": "3.3.7", "matchCriteriaId": "CF303B21-D9BF-461D-B7B0-A3FE1D557A9F"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.4.0", "versionEndExcluding": "3.4.5", "matchCriteriaId": "DCCE43D0-8F17-475D-9EE6-842F758A9905"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5.0", "versionEndExcluding": "3.5.6", "matchCriteriaId": "F6BC0271-444D-4597-BF05-DC60034EAA49"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6.0", "versionEndExcluding": "3.6.2", "matchCriteriaId": "4A9E621D-29D8-418A-BF37-BED333C14507"}]}]}], "references": [{"url": "https://github.com/openssl/openssl/commit/59c3b3158553ab53275bbbccca5cb305d591cf2e", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/openssl/openssl/commit/5a0b4930779cd2408880979db765db919da55139", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/openssl/openssl/commit/602542f2c0c2d5edb47128f93eac10b62aeeefb3", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/openssl/openssl/commit/a9d187dd1000130100fa7ab915f8513532cb3bb8", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/openssl/openssl/commit/d3a901e8d9f021f3e67d6cfbc12e768129862726", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://openssl ... (truncated)