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

> A stack buffer overflow in the Zephyr HL7800 modem driver allows remote attackers to cause crashes or execute code via malicious network responses.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Aug 2026
- **Updated:** 20 Aug 2026
- **Also known as:** GHSA-hchc-6489-w66v

## What is CVE-2026-12522?

CVE-2026-12522 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-12522?


## How do I fix CVE-2026-12522?

No fix has been published for CVE-2026-12522 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12522 being exploited?

There is no known exploitation of CVE-2026-12522 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12522 and fix it if it is affected.

What it is: CVE-2026-12522 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-12522 in the wild and no public exploit code.

Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-12522/ (Markdown: https://insights.sbomify.com/CVE-2026-12522/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12522
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12522
- OSV: https://osv.dev/vulnerability/CVE-2026-12522

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-12522/
Summaries are generated and may contain mistakes; the official description above is the record.