# CVE-2026-10646: Use-after-return in `zsock_getaddrinfo()` when a timed-out DNS query is retried without cancellation > An attacker can trigger a use-after-return in Zephyr's DNS resolver via spoofed responses, causing crashes or memory corruption. - **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 28 Jun 2026 - **Updated:** 15 Oct 2026 - **Also known as:** GHSA-h752-vhmf-29w6 ## What is CVE-2026-10646? CVE-2026-10646 is a high-severity use after free vulnerability in Zephyrproject Zephyr, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2026-10646? It affects 1 product. Products: Zephyrproject Zephyr. ## How do I fix CVE-2026-10646? No fix has been published for CVE-2026-10646 yet. Limit exposure of the affected software until one is available. ## Is CVE-2026-10646 being exploited? There is no known exploitation of CVE-2026-10646 in the wild and no public exploit code. ## 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-2026-10646 and fix it if it is affected. What it is: CVE-2026-10646 is a high-severity use after free vulnerability in Zephyrproject Zephyr, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-10646 in the wild and no public exploit code. 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-2026-10646/ (Markdown: https://insights.sbomify.com/CVE-2026-10646/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10646 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10646 - OSV: https://osv.dev/vulnerability/CVE-2026-10646 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-10646/ Summaries are generated and may contain mistakes; the official description above is the record.