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CVE-2026-12633— Out-of-bounds write in IPv6 6LoWPAN Context Option handling via unauthenticated Router Advertisement

Quick assessment

Affected
zephyrproject zephyr
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Zephyr Project Zephyr是Zephyr Project组织开源的一款面向物联网设备的实时操作系统。 Zephyr Project Zephyr 1.8.0至4.4.2之前版本存在缓冲区错误漏洞，该漏洞源于IPv6邻居发现代码在处理6LoWPAN Context Option时未对context_len字段进行有效限制，导致越界写入，可能造成远程拒绝服务和内存破坏。

CVSS 8.1 · High EPSS 0.21% · P12

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 1.8.0< 4.4.2 affected
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I. Basic Information for CVE-2026-12633

Vulnerability Information
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Vulnerability Title
Out-of-bounds write in IPv6 6LoWPAN Context Option handling via unauthenticated Router Advertisement
Source: CVE Program / CVE List V5
Vulnerability Description
The IPv6 neighbor-discovery code in subsys/net/ip/ipv6_nbr.c processes the 6LoWPAN Context Option (6CO, RFC 6775) carried inside ICMPv6 Router Advertisements. In handle_ra_6co() the 8-bit context_len field is taken directly from the packet and was never bounded to the RFC maximum of 128. The function computes context->context_len / 8 and then performs memset(context->prefix + context_len, 0, sizeof(context->prefix) - context_len), where context->prefix is a fixed 16-byte array. With context_len between 136 and 255 (and the option length field set to 3, which the pre-fix validation accepts), context_len / 8 evaluates to 17..31, so the memset length 16 - context_len/8 underflows the unsigned size_t argument to roughly SIZE_MAX. This produces an unbounded out-of-bounds memset that zeroes kernel memory well past the 6lo context structure. The defect is reachable from unauthenticated, link-local input: any host on the same link can send a crafted Router Advertisement with a 6CO option. The RA handler validates only the option length field before calling handle_ra_6co(), so a single packet triggers the wild write. The code is compiled when CONFIG_NET_6LO_CONTEXT is enabled. The impact is a reliable remote (adjacent) denial of service via memory corruption, with collateral integrity loss as the memset zeroes contiguous memory before the system faults. Router Advertisements are link-scoped and not forwarded, so the attacker must be on the same link (AV:A). The fix rejects any context_len greater than 128 before the length computation.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
Zephyr Project Zephyr 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Zephyr Project Zephyr是Zephyr Project组织开源的一款面向物联网设备的实时操作系统。 Zephyr Project Zephyr 1.8.0至4.4.2之前版本存在缓冲区错误漏洞，该漏洞源于IPv6邻居发现代码在处理6LoWPAN Context Option时未对context_len字段进行有效限制，导致越界写入，可能造成远程拒绝服务和内存破坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 1.8.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-12633

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III. Intelligence Information for CVE-2026-12633

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Patches & Fixes for CVE-2026-12633 (1)

Vendor Advisories for CVE-2026-12633 (1)

Same Patch Batch · zephyrproject · 2026-08-19 · 3 CVEs total

CVE-2026-12522 8.8 HIGH Stack buffer overflow in Zephyr hl7800 modem driver parsing network-supplied +CGCONTRDP ad
CVE-2026-12634 5.3 MEDIUM Out-of-bounds stack write in the settings NVS backend from over-reported nvs_read length

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-787

V. Comments for CVE-2026-12633

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