# CVE-2026-126957: ICMPv4 Record Route / Timestamp option: stack OOB read via ptr underflow in icmpv4.c

Status: published. Published: 2026-11-12. Updated: 2026-11-12.

An integer underflow in Zephyr's IPv4 option handling allows a remote, unauthenticated attacker to read stack memory. When replying to an ICMP Echo Request that carries an IPv4 Record Route or Timestamp option, icmpv4_update_record_route() and icmpv4_update_time_stamp() in subsys/net/ip/icmpv4.c compute the length of the already recorded data as ptr - ptr_offset in uint8_t arithmetic. The attacker-controlled Pointer field is checked against the option length but not against the RFC 791 minimum (4 for Record Route, 5 for Timestamp), so a smaller value wraps the length to up to 252 bytes. net_pkt_write() then reads past the 40-byte opt_data stack buffer and up to 213 bytes of stack memory, which can include stack and heap pointers, are returned in the ICMP Echo Reply. A single packet triggers the leak and the device does not crash, so it can be repeated. Devices built with CONFIG_NET_IPV4_HDR_OPTIONS, which CONFIG_NET_IPV4_IGMP selects, are affected.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- zephyrproject-rtos / Zephyr (Zephyr): ≤ 4.4.0 (affected, git). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: zephyr

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: zephyr

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-125, CWE-191, CWE-200

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cvv6-5f6x-87qf (CNA: zephyr)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-126957; retrieved 2026-11-12; source updated 2026-11-12

Revision: daf6c63db62dadd7814bad80852334a1903cd39d911a8ca8d7bd04963925afae

Canonical: https://y2.dev/cve/CVE-2026-126957

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