Description
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.
Published: 2026-11-12
Score: 6.9 Medium
EPSS: < 1% Very Low
KEV: No
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Remediation

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History

Thu, 12 Nov 2026 02:30:00 +0000

Type Values Removed Values Added
Description 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.
Title ICMPv4 Record Route / Timestamp option: stack OOB read via ptr underflow in icmpv4.c
Weaknesses CWE-125
CWE-191
CWE-200
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}

cvssV4_0

{'score': 6.9, 'vector': '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'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-11-12T02:23:44.385Z

Reserved: 2026-11-12T02:06:20.541Z

Link: CVE-2026-126957

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-12T03:17:11.617

Modified: 2026-11-12T03:17:11.617

Link: CVE-2026-126957

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-125

    Out-of-bounds Read

  • CWE-191

    Integer Underflow (Wrap or Wraparound)

  • CWE-200

    Exposure of Sensitive Information to an Unauthorized Actor