CVE-2026-10639 Use-after-free reading `net_pkt_iface()` of a sent ICMPv4 echo-reply packet in `icmpv4_handle_echo_request()`
Remote attackers can trigger a use-after-free in Zephyr's ICMPv4 stack, causing crashes or memory corruption when interface statistics are enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-10639?
CVE-2026-10639 is a medium-severity use after free vulnerability in Zephyrproject Zephyr, published on 16 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Zephyr's native IPv4 stack, icmpv4_handle_echo_request() in subsys/net/ip/icmpv4.c builds an echo-reply packet (reply), hands it to net_try_send_data(), and then, on success, calls net_stats_update_icmp_sent(net_pkt_iface(reply)). net_try_send_data() transfers ownership of reply to the TX path (net_if_try_queue_tx -> net_if_tx -> L2/driver send, or the asynchronous net_if_tx_thread), which can unref it to refcount 0 and return the struct net_pkt to its slab (net_pkt_unref -> k_mem_slab_free) before the stats line runs. net_core.c documents this exact contract ('the pkt might contain garbage already ... do not use pkt after that call').
The post-send net_pkt_iface(reply) therefore reads reply->iface out of a freed (and possibly already reallocated) net_pkt, a use-after-free read; with CONFIG_NET_STATISTICS_PER_INTERFACE the stats macro additionally increments a counter through that value, i.e. a dereference/write through a stale or recycled-slot pointer.
The path is reached unauthenticated by any remote host that pings the device (net_icmpv4_input -> net_icmp_call_ipv4_handlers -> icmpv4_handle_echo_request) and is gated on CONFIG_NET_STATISTICS_ICMP. Impact is a probabilistic read of recycled packet memory plus a possible wild-pointer write under a timing race, leading most likely to corrupted interface statistics or a remotely triggerable crash (DoS).
The defect was introduced in 2019 (v1.14) and is present through v4.4.0. The companion change in net_icmpv4_send_error() is not a use-after-free because it reads net_pkt_iface(orig), the caller-owned received packet, which stays alive across the send. The fix caches the interface pointer from the live received packet before sending and uses it for the post-send stats updates.
Weakness: CWE-416
Which versions are affected by CVE-2026-10639?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-10639?
No fix has been published for CVE-2026-10639 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-10639 being exploited?
There is no known exploitation of CVE-2026-10639 in the wild and no public exploit code.
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Sources
Also known as GHSA-qhrf-w466-qmpw.