# CVE-2026-12522: Stack buffer overflow in Zephyr hl7800 modem driver parsing network-supplied +CGCONTRDP address fields

Status: published. Published: 2026-08-19. Updated: 2026-11-04.

The HL7800 cellular modem driver's +CGCONTRDP: response handler on_cmd_atcmdinfo_ipaddr() in drivers/modem/vendor_standalone/hl7800.c parses the PDP-context dynamic parameters (local address, subnet mask, gateway, and DNS servers) that the cellular network assigns to the device. The response is linearized into a 256-byte stack buffer, after which each address field length is computed from comma/. delimiter positions in the network-supplied data and used directly as the length argument to strncpy() into the fixed 64-byte stack buffer temp_addr_str (and the 16-byte iface_ctx.dns_v4_string).

Because the field length is derived from attacker-controlled delimiter positions and was not bounded against the destination buffer, a single field can be far larger than 64 bytes. A malicious or impersonated cellular network (for example a rogue base station) can return a crafted +CGCONTRDP response with an overlong address field, causing strncpy() to write past temp_addr_str on the modem worker thread's stack, plus an out-of-bounds NUL write at temp_addr_str[addr_len].

No device-side privileges or user interaction are required: the device itself issues the AT+CGCONTRDP=1 query during normal network attach and parses whatever the network returns. The overflow corrupts adjacent stack memory in supervisor context, yielding at minimum a remotely triggerable crash and potentially control-flow hijacking on targets without stack protection.

The fix bounds every field length against its destination buffer (temp_addr_str and dns_v4_string) before each copy, rejecting overlong fields.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/a1cbced64181bc0bdf95e1fd7118f2bb70cf679b

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 2.4.0; < 4.3.2 (affected, semver); ≥ 4.4.0; < 4.4.2 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: zephyr

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: NVD: vulnerabilities@zephyrproject.org

- CISA KEV: No listing in collected sources

- EPSS: 0.34% as of 2026-11-03; percentile 27.60%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-787

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/a1cbced64181bc0bdf95e1fd7118f2bb70cf679b (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-hchc-6489-w66v (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/commit/a1cbced64181bc0bdf95e1fd7118f2bb70cf679b (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-hchc-6489-w66v (vulnerabilities@zephyrproject.org)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-12522; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12522; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-12522; retrieved 2026-11-04; source updated Not reported

Revision: cdc8ff6fc3063b97be5fe0b052dc2ad39da095791f3d8d5e061982639e789981

Canonical: https://y2.dev/cve/CVE-2026-12522

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