CVE-2026-12633

See a problem?
Please try reporting it to the source first.

Source

https://cve.org/CVERecord?id=CVE-2026-12633

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12633.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-12633

Aliases

GHSA-h5m5-hm6j-cgpf

Published

2026-08-19T20:37:34.532Z

Modified

2026-08-22T09:15:48.277590Z

Severity

8.1 (High) CVSS_V3 - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H CVSS Calculator

Summary

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

Details

The IPv6 neighbor-discovery code in subsys/net/ip/ipv6nbr.c processes the 6LoWPAN Context Option (6CO, RFC 6775) carried inside ICMPv6 Router Advertisements. In handlera6co() the 8-bit contextlen field is taken directly from the packet and was never bounded to the RFC maximum of 128. The function computes context->contextlen / 8 and then performs memset(context->prefix + contextlen, 0, sizeof(context->prefix) - context_len), where context->prefix is a fixed 16-byte array.

With contextlen between 136 and 255 (and the option length field set to 3, which the pre-fix validation accepts), contextlen / 8 evaluates to 17..31, so the memset length 16 - contextlen/8 underflows the unsigned sizet 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 handlera6co(), so a single packet triggers the wild write. The code is compiled when CONFIGNET6LO_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.

Database specific

{
    "cwe_ids": [
        "CWE-787"
    ],
    "cna_assigner": "zephyr",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12633.json"
}

References

Affected packages

Git / github.com/zephyrproject-rtos/zephyr

Affected ranges

Type

GIT

Repo

https://github.com/zephyrproject-rtos/zephyr

Events

Introduced

fcb9144dca68f98d24caf39532595555355c3c1d

Fixed

15e838c739be637bf23fd56a5c26f2b32079551b

Database specific

Show details

{
    "source": [
        "AFFECTED_FIELD",
        "REFERENCES"
    ],
    "extracted_events": [
        {
            "introduced": "1.8.0"
        },
        {
            "fixed": "4.4.2"
        }
    ]
}

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12633.json"

vanir_signatures

[
    {
        "signature_type": "Function",
        "digest": {
            "function_hash": "267539371696623121120350077775344467726",
            "length": 604.0
        },
        "target": {
            "function": "handle_ra_6co",
            "file": "subsys/net/ip/ipv6_nbr.c"
        },
        "source": "https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b",
        "signature_version": "v1",
        "id": "CVE-2026-12633-3b7fcb39",
        "deprecated": false
    },
    {
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "204206096444958091730372478603137950800",
                "338615262403669516417959998986501470228",
                "85139857402039309434835499307801015552",
                "271653168381252246532307486393129816758",
                "20062006815393758460042036162702769065"
            ]
        },
        "target": {
            "file": "subsys/net/ip/ipv6_nbr.c"
        },
        "source": "https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b",
        "signature_version": "v1",
        "id": "CVE-2026-12633-8142ab50",
        "deprecated": false
    }
]

vanir_signatures_modified

"2026-08-22T09:15:48Z"