# CVE-2026-10637: Use-after-free of `net_pkt` in IPv6 MLD send path triggerable by a link-local MLD Query

> Remote attackers can cause denial of service or potential memory corruption in Zephyr RTOS by sending a crafted MLD Query, exploiting a use-after-free in the IPv6 stack.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jun 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-m23w-34pp-4h92

## What is CVE-2026-10637?

CVE-2026-10637 is a medium-severity use after free vulnerability in Zephyrproject Zephyr, published on 16 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

subsys/net/ip/ipv6_mld.c:mld_send() read the packet interface via net_pkt_iface(pkt) after net_send_data(pkt) returned successfully. Per the network stack's ownership contract (include/zephyr/net/net_core.h, and the explicit warning in subsys/net/ip/net_core.c:453-460 'do not use pkt after that call'), a successful send transfers ownership of the net_pkt and the L2 driver frees it (e.g. ethernet_send() unrefs the packet on success, subsys/net/l2/ethernet/ethernet.c:790), returning it to its k_mem_slab.

The subsequent net_pkt_iface(pkt) is therefore a read of a freed object; the recovered interface pointer is then dereferenced and incremented by the per-interface statistics path (net_stats.h UPDATE_STAT/SET_STAT) when CONFIG_NET_STATISTICS_PER_INTERFACE is enabled. If the freed slot is concurrently reallocated, pkt->iface may read back as NULL (NULL-pointer dereference / crash) or as a stale/garbage pointer (stray increment write / memory corruption).

The path is reachable remotely on the local link without authentication: handle_mld_query() (registered for NET_ICMPV6_MLD_QUERY) responds to a valid MLDv2 General Query (unspecified multicast address, hop limit 1) by calling send_mld_report() -> mld_send().

The result is a remotely triggerable denial of service of the networking stack, with a narrow possibility of memory corruption. The fix caches the interface in a local before sending and no longer touches the packet after net_send_data(). The IPv4/IGMP sibling (igmp_send) already used the corrected pattern.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-10637?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-10637?

No fix has been published for CVE-2026-10637 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10637 being exploited?

There is no known exploitation of CVE-2026-10637 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-2026-10637 and fix it if it is affected.

What it is: CVE-2026-10637 is a medium-severity use after free vulnerability in Zephyrproject Zephyr, published on 16 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-10637 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-2026-10637/ (Markdown: https://insights.sbomify.com/CVE-2026-10637/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10637
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10637
- OSV: https://osv.dev/vulnerability/CVE-2026-10637

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-10637/
Summaries are generated and may contain mistakes; the official description above is the record.