CVE-2026-10646

CVE-2026-10646 is a high-severity vulnerability in Zephyrproject Zephyr with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.

Key facts

Description

Zephyr's BSD-sockets getaddrinfo() implementation (subsys/net/lib/sockets/getaddrinfo.c) passes a pointer to a stack-allocated state object (struct getaddrinfo_state ai_state) as the user_data of an asynchronous DNS resolver query. The socket layer waits on a semaphore with a timeout deliberately set slightly longer than the resolver's own per-query timeout. When that semaphore wait nonetheless times out (-EAGAIN) - which can occur when the resolver's timeout work is delayed by workqueue contention, or in the documented multi-retry configuration where CONFIG_NET_SOCKETS_DNS_TIMEOUT exceeds CONFIG_NET_SOCKETS_DNS_BACKOFF_INTERVAL - the pre-fix code retries the query (goto again) without cancelling the previous one and without resetting the semaphore. The previous query slot remains active in the resolver with its callback and the stack pointer as user_data, and ai_state-dns_id is overwritten so the stale query can no longer be cancelled. A subsequent DNS response delivered over UDP and matched by its 16-bit transaction id (in dispatcher_cb()/dns_read()), or the resolver's own delayed query-timeout work, then invokes dns_resolve_cb() against the now out-of-scope stack frame, writing through the stale pointer (state-status, state-idx, state-ai_arr[], and k_sem_give()). Because the triggering response is network-delivered and its 16-bit id is spoofable/replayable by an on- or off-path attacker, this is a network-influenceable use-after-return that can corrupt reused stack memory, leading to crashes/denial of service or memory corruption. The fix cancels the timed-out query by name and type before retrying and resets the local semaphore, eliminating the stale callback path. Affected: Zephyr v4.0.0 through v4.4.0.

Frequently asked questions

What is CVE-2026-10646?
Zephyr's BSD-sockets getaddrinfo() implementation (subsys/net/lib/sockets/getaddrinfo.c) passes a pointer to a stack-allocated state object (struct getaddrinfo_state ai_state) as the user_data of an asynchronous DNS resolver query. The socket layer waits on a semaphore with a timeout deliberately set slightly longer than the resolver's own per-query timeout. When that semaphore wait nonetheless times out (-EAGAIN) - which can occur when the resolver's timeout work is delayed by workqueue contention, or in the documented multi-retry configuration where CONFIG_NET_SOCKETS_DNS_TIMEOUT exceeds CONFIG_NET_SOCKETS_DNS_BACKOFF_INTERVAL - the pre-fix code retries the query (goto again) without cancelling the previous one and without resetting the semaphore. The previous query slot remains active in the resolver with its callback and the stack pointer as user_data, and ai_state-dns_id is overwritten so the stale query can no longer be cancelled. A subsequent DNS response delivered over UDP and matched by its 16-bit transaction id (in dispatcher_cb()/dns_read()), or the resolver's own delayed query-timeout work, then invokes dns_resolve_cb() against the now out-of-scope stack frame, writing through the stale pointer (state-status, state-idx, state-ai_arr[], and k_sem_give()). Because the triggering response is network-delivered and its 16-bit id is spoofable/replayable by an on- or off-path attacker, this is a network-influenceable use-after-return that can corrupt reused stack memory, leading to crashes/denial of service or memory corruption. The fix cancels the timed-out query by name and type before retrying and resets the local semaphore, eliminating the stale callback path. Affected: Zephyr v4.0.0 through v4.4.0.
How severe is CVE-2026-10646?
CVE-2026-10646 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2026-10646 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-10646?
CVE-2026-10646 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-10646?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-10646 published?
CVE-2026-10646 was published on 2026-06-28 and last updated on 2026-07-06.

References

Affected products (1)

More vulnerabilities in Zephyrproject Zephyr

All CVEs affecting Zephyrproject Zephyr →

Other CWE-416 (Use After Free) vulnerabilities

Browse all CWE-416 (Use After Free) vulnerabilities →