Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
zephyrproject zephyr — Use-after-free race in SNTP async client when closing the socket while the socket service is still polling it
AV AC PR UI S C I A CVSS EPSS %ile KEV
N H N N U N N H 5.9 .0030 22.8 —
AFFECTED
Product Versions Fixed
zephyr 4.2.0 – —
TIMELINE
Jun 2 Reserved by zephyr
Jun 30 EXPLOIT PUBLISHED — CVE-2026-10655 (zephyrproject zephyr). Public exploit reference added.
Jun 30 Published (CNA: zephyr)
Description
The asynchronous SNTP client in Zephyr (subsys/net/lib/sntp/sntp.c, sntp_close_async) closed the UDP socket file descriptor directly from the calling thread immediately after detaching it from the network socket service, without synchronizing with the socket-service poll thread.
The socket service thread polls each socket via zvfs_poll, which (in zsock_poll_prepare_ctx) registers a k_poll_event pointing into the socket's net_context (&ctx->recv_q) and then blocks in k_poll without holding a reference or lock. net_context objects are allocated from a fixed pool (contexts[CONFIG_NET_MAX_CONTEXTS]) and reused after close.
When sntp_close_async is invoked from a different thread than the poll thread (in the in-tree consumer subsys/net/lib/config/init_clock_sntp.c, the SNTP timeout handler runs on the system workqueue while the socket service thread is blocked in poll on the same fd), the close frees and may reuse the net_context while the poll thread still has a poller node linked into the freed object, resulting in a use-after-free / object confusion of kernel poll structures.
The SNTP timeout path is the normal no-response failure mode, so a network peer or off-path attacker who drops or delays the SNTP/NTP response can drive the racing close repeatedly (and periodically with NET_CONFIG_SNTP_INIT_RESYNC). The most likely consequence is a crash of the networking thread (denial of service), with potential memory corruption when the freed context slot is reallocated.
The fix defers the close to the socket service thread itself via net_socket_service_close (NET_SOCKET_SERVICE_CLOSE_SOCKETS), so the same thread that polls performs the close, eliminating the race. Affected releases: v4.2.0 through v4.4.0.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| June 2, 2026 | Reserved | Reserved by zephyr |
| June 30, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-10655 (zephyrproject zephyr). Public exploit reference added. |
| June 30, 2026 | Published | Published (CNA: zephyr) |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| zephyrproject | zephyr | — | 4.2.0 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-10655 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.