# CVE-2026-10773: Out-of-bounds read in DHCPv4 client message-type name lookup (net_dhcpv4_msg_type_name)

> A remote attacker can cause a crash or leak memory in Zephyr RTOS DHCPv4 clients by sending malformed packets when debug logging is enabled.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L`)
- **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:** 1 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-r5hq-xq42-wcfq

## What is CVE-2026-10773?

CVE-2026-10773 is a medium-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 1 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The DHCPv4 client helper net_dhcpv4_msg_type_name() in subsys/net/lib/dhcpv4/dhcpv4.c indexes a static 8-element const char * name table after a faulty bounds check. The guard used msg_type <= sizeof(name) instead of msg_type <= ARRAY_SIZE(name); sizeof returns the byte size of the pointer array (32 on 32-bit, 64 on 64-bit targets) rather than the element count of 8, so message-type values from 9 up to that byte size pass the check and cause name[msg_type - 1] to read past the end of the array.

The msg_type value originates from the DHCP MESSAGE TYPE option, which is read as an unchecked raw byte from a received packet (net_pkt_read_u8) and passed unmodified into the lookup. A DHCP server, or any host able to inject a spoofed DHCP reply onto the client's link, can therefore drive the index out of bounds. The out-of-range slot yields a garbage const char * that is then dereferenced by a %s log conversion.

The lookup is reached only from a debug log statement (NET_DBG / LOG_DBG), so the out-of-bounds read is triggerable only when the DHCPv4 log module is built at DEBUG level (CONFIG_NET_DHCPV4_LOG_LEVEL_DBG), which is not the default configuration. When that condition holds, the result is an out-of-bounds read and a wild-pointer dereference: most likely a crash of the DHCP client (denial of service) and potentially disclosure of an adjacent pointer's contents through the log output. The fix replaces sizeof with ARRAY_SIZE, restoring the correct 1..8 acceptance window.

Weakness: CWE-682 (Incorrect Calculation), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-10773?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-10773?

No fix has been published for CVE-2026-10773 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10773 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10773 exists.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2026-5067](https://insights.sbomify.com/CVE-2026-5067/): Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key (critical 9.8)
- [CVE-2022-3806](https://insights.sbomify.com/CVE-2022-3806/): Bluetooth HCI Error Handling Double Free (critical 9.8)
- [CVE-2017-14199](https://insights.sbomify.com/CVE-2017-14199/): Memory corruption in getaddrinfo (critical 9.8)
- [CVE-2018-1000800](https://insights.sbomify.com/CVE-2018-1000800/): Null dereference in n/a (critical 9.8)
- [CVE-2021-3329](https://insights.sbomify.com/CVE-2021-3329/): DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-10773 and fix it if it is affected.

What it is: CVE-2026-10773 is a medium-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 1 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10773 exists.

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-2026-10773/ (Markdown: https://insights.sbomify.com/CVE-2026-10773/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10773
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10773
- OSV: https://osv.dev/vulnerability/CVE-2026-10773

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-10773/
Summaries are generated and may contain mistakes; the official description above is the record.