Vulnerability-Lookup

CVE-2026-12520 (GCVE-0-2026-12520)

Vulnerability from cvelistv5 – Published: 2026-08-18 19:41 – Updated: 2026-08-18 19:41

Title

Stack buffer overflow and off-by-one writes in Zephyr HL7800 modem AT response handlers

Summary

The Sierra Wireless HL7800 cellular modem driver (drivers/modem/vendor_standalone/hl7800.c, located at drivers/modem/hl7800.c in v4.4.0 and earlier) parses AT responses with roughly twenty handlers that call net_buf_linearize(value, sizeof(value), *buf, 0, len) into a 128-byte stack buffer and then write value[out_len] = 0. Because net_buf_linearize() (lib/net_buf/buf.c) can return a count equal to its destination-length argument, a field that exactly fills the buffer makes the terminating NUL land one byte past the end, a single-byte out-of-bounds write into adjacent stack memory. The +KCELLMEAS cell-measurement handler on_cmd_atcmdinfo_rssi() is worse: it passed the wire length len as the destination size (net_buf_linearize(value, len, *buf, 0, len)), so a response line longer than 128 bytes overflows the value stack buffer with attacker-influenceable content. The line length comes from net_buf_findcrlf(), which accumulates bytes across the whole net_buf fragment chain and is not bounded to 128, so an over-long line reaches the defect. The data originates from the cellular modem over UART, driven by the network: operator-scan results, +CGCONTRDP IP/DNS info, socket indications, and +KCELLMEAS neighbour-cell reports. An attacker able to shape what the modem emits — a rogue base station, a compromised modem baseband, or a remote peer feeding oversized response framing — can drive a line past 128 bytes. The handlers run in the driver's RX thread in kernel context, so the corruption is kernel-side. The +KCELLMEAS path is a full stack buffer overflow whose worst case is code execution in kernel context and whose floor is a reliable crash; the remaining sites are single-byte NUL out-of-bounds writes. Exploitation requires the modem to emit an over-long AT response line, giving high attack complexity over an adjacent (cellular radio) vector. The fix passes sizeof(dst) - 1 (and correct explicit bounds for the IMSI and +KCELLMEAS sites) so the terminator always stays in bounds.

Severity

6.4 (Medium)


                        
                          CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

CWE

CWE-787 - memory-safety

Assigner

zephyr mitre root

References

2 references

URL	Tags
https://github.com/zephyrproject-rtos/zephyr/comm…	patch
https://github.com/zephyrproject-rtos/zephyr/secu…

Impacted products

1 product

Vendor	Product	Version	CPE status
zephyrproject	zephyr	Affected: 2.4.0 , < 4.4.2 (semver)	guessed

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
          "defaultStatus": "unaffected",
          "packageName": "zephyr",
          "product": "zephyr",
          "programFiles": [
            "drivers/modem/vendor_standalone/hl7800.c"
          ],
          "vendor": "zephyrproject",
          "versions": [
            {
              "lessThan": "4.4.2",
              "status": "affected",
              "version": "2.4.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "The Sierra Wireless HL7800 cellular modem driver (drivers/modem/vendor_standalone/hl7800.c, located at drivers/modem/hl7800.c in v4.4.0 and earlier) parses AT responses with roughly twenty handlers that call net_buf_linearize(value, sizeof(value), *buf, 0, len) into a 128-byte stack buffer and then write value[out_len] = 0. Because net_buf_linearize() (lib/net_buf/buf.c) can return a count equal to its destination-length argument, a field that exactly fills the buffer makes the terminating NUL land one byte past the end, a single-byte out-of-bounds write into adjacent stack memory.\n\nThe +KCELLMEAS cell-measurement handler on_cmd_atcmdinfo_rssi() is worse: it passed the wire length len as the destination size (net_buf_linearize(value, len, *buf, 0, len)), so a response line longer than 128 bytes overflows the value stack buffer with attacker-influenceable content. The line length comes from net_buf_findcrlf(), which accumulates bytes across the whole net_buf fragment chain and is not bounded to 128, so an over-long line reaches the defect.\n\nThe data originates from the cellular modem over UART, driven by the network: operator-scan results, +CGCONTRDP IP/DNS info, socket indications, and +KCELLMEAS neighbour-cell reports. An attacker able to shape what the modem emits \u2014 a rogue base station, a compromised modem baseband, or a remote peer feeding oversized response framing \u2014 can drive a line past 128 bytes. The handlers run in the driver\u0027s RX thread in kernel context, so the corruption is kernel-side.\n\nThe +KCELLMEAS path is a full stack buffer overflow whose worst case is code execution in kernel context and whose floor is a reliable crash; the remaining sites are single-byte NUL out-of-bounds writes. Exploitation requires the modem to emit an over-long AT response line, giving high attack complexity over an adjacent (cellular radio) vector. The fix passes sizeof(dst) - 1 (and correct explicit bounds for the IMSI and +KCELLMEAS sites) so the terminator always stays in bounds."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 6.4,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-787",
              "description": "memory-safety",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-18T19:41:07.446Z",
        "orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
        "shortName": "zephyr"
      },
      "references": [
        {
          "name": "Fix commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/zephyrproject-rtos/zephyr/commit/ea91f9375677aa4268e4044e096902dbe789f101"
        },
        {
          "name": "GHSA-9xc4-j5x8-v6jx",
          "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-9xc4-j5x8-v6jx"
        }
      ],
      "title": "Stack buffer overflow and off-by-one writes in Zephyr HL7800 modem AT response handlers",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
    "assignerShortName": "zephyr",
    "cveId": "CVE-2026-12520",
    "datePublished": "2026-08-18T19:41:07.446Z",
    "dateReserved": "2026-06-17T12:59:12.042Z",
    "dateUpdated": "2026-08-18T19:41:07.446Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-12520\",\"sourceIdentifier\":\"vulnerabilities@zephyrproject.org\",\"published\":\"2026-08-18T20:17:11.660\",\"lastModified\":\"2026-08-18T20:17:11.660\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"The Sierra Wireless HL7800 cellular modem driver (drivers/modem/vendor_standalone/hl7800.c, located at drivers/modem/hl7800.c in v4.4.0 and earlier) parses AT responses with roughly twenty handlers that call net_buf_linearize(value, sizeof(value), *buf, 0, len) into a 128-byte stack buffer and then write value[out_len] = 0. Because net_buf_linearize() (lib/net_buf/buf.c) can return a count equal to its destination-length argument, a field that exactly fills the buffer makes the terminating NUL land one byte past the end, a single-byte out-of-bounds write into adjacent stack memory.\\n\\nThe +KCELLMEAS cell-measurement handler on_cmd_atcmdinfo_rssi() is worse: it passed the wire length len as the destination size (net_buf_linearize(value, len, *buf, 0, len)), so a response line longer than 128 bytes overflows the value stack buffer with attacker-influenceable content. The line length comes from net_buf_findcrlf(), which accumulates bytes across the whole net_buf fragment chain and is not bounded to 128, so an over-long line reaches the defect.\\n\\nThe data originates from the cellular modem over UART, driven by the network: operator-scan results, +CGCONTRDP IP/DNS info, socket indications, and +KCELLMEAS neighbour-cell reports. An attacker able to shape what the modem emits \u2014 a rogue base station, a compromised modem baseband, or a remote peer feeding oversized response framing \u2014 can drive a line past 128 bytes. The handlers run in the driver\u0027s RX thread in kernel context, so the corruption is kernel-side.\\n\\nThe +KCELLMEAS path is a full stack buffer overflow whose worst case is code execution in kernel context and whose floor is a reliable crash; the remaining sites are single-byte NUL out-of-bounds writes. Exploitation requires the modem to emit an over-long AT response line, giving high attack complexity over an adjacent (cellular radio) vector. The fix passes sizeof(dst) - 1 (and correct explicit bounds for the IMSI and +KCELLMEAS sites) so the terminator always stays in bounds.\"}],\"affected\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"affectedData\":[{\"vendor\":\"zephyrproject\",\"product\":\"zephyr\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://github.com/zephyrproject-rtos/zephyr\",\"packageName\":\"zephyr\",\"programFiles\":[\"drivers/modem/vendor_standalone/hl7800.c\"],\"versions\":[{\"version\":\"2.4.0\",\"lessThan\":\"4.4.2\",\"versionType\":\"semver\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H\",\"baseScore\":6.4,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"ADJACENT_NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.6,\"impactScore\":4.7}]},\"weaknesses\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]}],\"references\":[{\"url\":\"https://github.com/zephyrproject-rtos/zephyr/commit/ea91f9375677aa4268e4044e096902dbe789f101\",\"source\":\"vulnerabilities@zephyrproject.org\"},{\"url\":\"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-9xc4-j5x8-v6jx\",\"source\":\"vulnerabilities@zephyrproject.org\"}]}}"
  }
}

FKIE_CVE-2026-12520

Vulnerability from fkie_nvd - Published: 2026-08-18 20:17 - Updated: 2026-08-18 20:17

Severity

6.4 (Medium) - CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

Summary

References

	URL	Tags
	vulnerabilities@zephyrproject.org	https://github.com/zephyrproject-rtos/zephyr/commit/ea91f9375677aa4268e4044e096902dbe789f101
	vulnerabilities@zephyrproject.org	https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-9xc4-j5x8-v6jx

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
          "defaultStatus": "unaffected",
          "packageName": "zephyr",
          "product": "zephyr",
          "programFiles": [
            "drivers/modem/vendor_standalone/hl7800.c"
          ],
          "vendor": "zephyrproject",
          "versions": [
            {
              "lessThan": "4.4.2",
              "status": "affected",
              "version": "2.4.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "vulnerabilities@zephyrproject.org"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The Sierra Wireless HL7800 cellular modem driver (drivers/modem/vendor_standalone/hl7800.c, located at drivers/modem/hl7800.c in v4.4.0 and earlier) parses AT responses with roughly twenty handlers that call net_buf_linearize(value, sizeof(value), *buf, 0, len) into a 128-byte stack buffer and then write value[out_len] = 0. Because net_buf_linearize() (lib/net_buf/buf.c) can return a count equal to its destination-length argument, a field that exactly fills the buffer makes the terminating NUL land one byte past the end, a single-byte out-of-bounds write into adjacent stack memory.\n\nThe +KCELLMEAS cell-measurement handler on_cmd_atcmdinfo_rssi() is worse: it passed the wire length len as the destination size (net_buf_linearize(value, len, *buf, 0, len)), so a response line longer than 128 bytes overflows the value stack buffer with attacker-influenceable content. The line length comes from net_buf_findcrlf(), which accumulates bytes across the whole net_buf fragment chain and is not bounded to 128, so an over-long line reaches the defect.\n\nThe data originates from the cellular modem over UART, driven by the network: operator-scan results, +CGCONTRDP IP/DNS info, socket indications, and +KCELLMEAS neighbour-cell reports. An attacker able to shape what the modem emits \u2014 a rogue base station, a compromised modem baseband, or a remote peer feeding oversized response framing \u2014 can drive a line past 128 bytes. The handlers run in the driver\u0027s RX thread in kernel context, so the corruption is kernel-side.\n\nThe +KCELLMEAS path is a full stack buffer overflow whose worst case is code execution in kernel context and whose floor is a reliable crash; the remaining sites are single-byte NUL out-of-bounds writes. Exploitation requires the modem to emit an over-long AT response line, giving high attack complexity over an adjacent (cellular radio) vector. The fix passes sizeof(dst) - 1 (and correct explicit bounds for the IMSI and +KCELLMEAS sites) so the terminator always stays in bounds."
    }
  ],
  "id": "CVE-2026-12520",
  "lastModified": "2026-08-18T20:17:11.660",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "ADJACENT_NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 6.4,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.6,
        "impactScore": 4.7,
        "source": "vulnerabilities@zephyrproject.org",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-18T20:17:11.660",
  "references": [
    {
      "source": "vulnerabilities@zephyrproject.org",
      "url": "https://github.com/zephyrproject-rtos/zephyr/commit/ea91f9375677aa4268e4044e096902dbe789f101"
    },
    {
      "source": "vulnerabilities@zephyrproject.org",
      "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-9xc4-j5x8-v6jx"
    }
  ],
  "sourceIdentifier": "vulnerabilities@zephyrproject.org",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "vulnerabilities@zephyrproject.org",
      "type": "Secondary"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-12520 (GCVE-0-2026-12520)

FKIE_CVE-2026-12520

Tags

Sightings

Nomenclature