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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
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.
Which versions are affected by CVE-2026-10773?
It affects 1 product.
Products include 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.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-10773 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10773 exists.
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Sources
Also known as GHSA-r5hq-xq42-wcfq.