Bluetooth OTS server discloses uninitialized stack memory in failed Calculate Checksum responses

{
  "id": "96fffe8d926b5b0503290b21934e88890d91ee2ddd1268b2557f744961e5d0b0",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-81038",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Bluetooth OTS server discloses uninitialized stack memory in failed Calculate Checksum responses",
    "summary": "The Object Transfer Service server builds its Object Action Control Point (OACP) response indication in oacp_ind_send() (subsys/bluetooth/services/ots/ots_oacp.c). Before this fix the four-byte Checksum Value field was appended whenever the requested op code was BT_GATT_OTS_OACP_PROC_CHECKSUM_CALC, regardless of the result code. The response payload is a bare, uninitialized four-byte stack buffer declared with NET_BUF_SIMPLE_DEFINE(resp_param, sizeof(uint32_t)) in bt_gatt_ots_oacp_write(), and it is filled only on the success path of oacp_checksum_proc_validate(). On every failure path the buffer is still empty, so net_buf_simple_pull_le32() was invoked on a zero-length buffer. The OACP characteristic and its client characteristic configuration descriptor are declared with BT_GATT_PERM_WRITE and BT_GATT_PERM_READ | BT_GATT_PERM_WRITE, so no pairing, encryption, or authentication is required. Any peer within radio range that can connect to a device running the OTS server can enable OACP indications and write a nine-byte Calculate Checksum command that fails validation — for example by issuing it with no object selected, which returns BT_GATT_OTS_OACP_RES_INV_OBJ. Because oacp_command_decode() accepts the Calculate Checksum op code unconditionally (it is not guarded by CONFIG_BT_OTS_OACP_CHECKSUM_SUPPORT), builds without checksum support are reachable too: they answer BT_GATT_OTS_OACP_RES_OPCODE_NOT_SUP and take the same bad path. On builds with CONFIG_ASSERT enabled, the zero-",
    "evidence": "cve:CVE-2026-81038",
    "products": [
      {
        "name": {
          "value": "zephyr",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-81038",
      "aliases": [
        "CVE-2026-81038"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV3_1": {
            "version": "3.1",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H"
          }
        }
      ],
      "affected": [
        {
          "vendor": "zephyrproject",
          "product": "zephyr",
          "versions": [
            {
              "status": "affected",
              "version": "3.3.0",
              "versionType": "semver",
              "lessThanOrEqual": "4.4.2"
            }
          ],
          "packageName": "zephyr",
          "programFiles": [
            "subsys/bluetooth/services/ots/ots_oacp.c"
          ],
          "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "bt_gatt_ots_oacp_write"
            },
            {
              "name": "oacp_ind_send"
            }
          ]
        }
      ],
      "modified": "2026-10-26T17:37:11.149Z",
      "provider": "cve",
      "references": [
        "https://github.com/zephyrproject-rtos/zephyr/commit/36145a6f1164e2e0a18c8c83d5b1be6e7d3f6e23",
        "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-7c9w-mhqw-5g86"
      ],
      "provider_metadata": {
        "adp": [
          {
            "title": "CISA ADP Vulnrichment",
            "metrics": [
              {
                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-81038",
                    "role": "CISA Coordinator",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "version": "2.0.3",
                    "timestamp": "2026-10-26T16:59:04.554659Z"
                  }
                }
              }
            ],
            "providerMetadata": {
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP",
              "dateUpdated": "2026-10-26T17:37:11.149Z"
            }
          }
        ],
        "cna": {
          "orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
          "shortName": "zephyr",
          "dateUpdated": "2026-10-26T16:08:50.091Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-81038",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 326392,
  "published_at": "2026-10-26T16:08:50.091+00:00"
}