OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()

{
  "id": "8fd8164292fcd15eb0db731b380faa7699d4b53945a3636f8159fe20ca203014",
  "url": "https://osv.dev/vulnerability/CVE-2026-33662",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()",
    "summary": "OP-TEE is a Trusted Execution Environment (TEE) designed as companion to a non-secure Linux kernel running on Arm; Cortex-A cores using the TrustZone technology. From 3.8.0 to 4.10, in the function emsa_pkcs1_v1_5_encode() in core/drivers/crypto/crypto_api/acipher/rsassa.c, the amount of padding needed, \"PS size\", is calculated by subtracting the size of the digest and other fields required for the EMA-PKCS1-v1_5 encoding from the size of the modulus of the key. By selecting a small enough modulus, this subtraction can overflow. The padding is added as a string of 0xFF bytes with a call to memset(), and an underflowed integer will cause the memset() call to overwrite until OP-TEE crashes. This only affects platforms registering RSA acceleration.",
    "evidence": "osv:CVE-2026-33662",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-33662",
      "aliases": [
        "CVE-2026-33662",
        "GHSA-4cf8-v5g3-73gr"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/op-tee/optee_os",
              "type": "GIT",
              "events": [
                {
                  "introduced": "023e33656e2c9557ce50ad63a98b2e2c9b51c118"
                },
                {
                  "last_affected": "753afbbee1682f5d16fd30e87b31058a4fd4f4b8"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "3.8.0"
                      },
                      {
                        "last_affected": "4.10"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  }
                ]
              }
            }
          ],
          "versions": [
            "4.10.0",
            "4.10.0-rc1",
            "4.9.0",
            "4.9.0-rc1",
            "4.8.0",
            "4.8.0-rc1",
            "4.7.0",
            "4.7.0-rc1",
            "4.6.0",
            "4.6.0-rc1",
            "4.5.0",
            "4.5.0-rc1",
            "4.4.0",
            "4.4.0-rc1",
            "4.3.0",
            "4.3.0-rc1",
            "4.2.0",
            "4.2.0-rc1",
            "4.1.0",
            "4.1.0-rc1",
            "4.0.0",
            "4.0.0-rc1",
            "3.22.0",
            "3.22.0-rc1",
            "3.21.0",
            "3.21.0-rc1",
            "3.20.0",
            "3.20.0-rc1",
            "3.19.0",
            "3.19.0-rc1",
            "3.18.0",
            "3.18.0-rc1",
            "3.17.0",
            "3.17.0-rc1",
            "3.16.0",
            "3.15.0",
            "3.15.0-rc1",
            "3.14.0",
            "3.14.0-rc1",
            "3.13.0",
            "3.13.0-rc1",
            "3.12.0",
            "3.12.0-rc1",
            "3.11.0",
            "3.11.0-rc1",
            "3.10.0",
            "3.10.0-rc1",
            "3.9.0",
            "3.9.0-rc1",
            "3.8.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33662.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.389451829Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33662.json",
        "https://github.com/OP-TEE/optee_os/security/advisories/GHSA-4cf8-v5g3-73gr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33662"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-190"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33662.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33662",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500460,
  "published_at": "2026-04-24T18:13:28.529+00:00"
}