{"cve":{"cve_id":"CVE-2026-12633","is_kev":false,"kev_date_added":null,"kev_vendor_project":null,"kev_product":null,"kev_vulnerability_name":null,"kev_short_description":null,"kev_required_action":null,"kev_due_date":null,"kev_known_ransomware":null,"kev_notes":null,"kev_cwes":null,"epss_score":0.00312,"epss_percentile":0.22467,"epss_as_of":"2026-10-15","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.\n\nWith 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.\n\nThe 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.\n\nThe 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.","published_at":"2026-08-19T20:37:34.532000Z","last_modified_at":"2026-08-26T16:59:23.267000Z","cvss_v3_score":8.1,"cvss_v3_vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","cvss_v3_severity":"HIGH","cvss_v4_score":null,"cvss_v4_vector":null,"cvss_v4_severity":null,"ssvc_decision":null,"ssvc_exploitation":"none","ssvc_automatable":false,"ssvc_technical_impact":"partial","cwes":["CWE-787"],"nvd_references":["https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b","https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-h5m5-hm6j-cgpf"],"vuln_status":"Awaiting Analysis","trending_score":null,"is_trending":false,"has_trended":false,"trended_number_one":false,"trending_peak_score":null,"trending_peak_rank":null,"started_trending_at":null,"trended_number_one_at":null,"summary_generated":null,"summary_generated_at":null,"summary_model":null,"created_at":"2026-08-19T21:42:27.531753Z","updated_at":"2026-08-27T18:05:39.505320Z"},"effective_severity":"HIGH","badges":[],"impact_analysis":[],"cvss_v3_decoded":{"version":"3.1","metrics":[{"metric":"AV","name":"Attack Vector","value":"A","value_label":"Adjacent"},{"metric":"AC","name":"Attack Complexity","value":"L","value_label":"Low"},{"metric":"PR","name":"Privileges Required","value":"N","value_label":"None"},{"metric":"UI","name":"User Interaction","value":"N","value_label":"None"},{"metric":"S","name":"Scope","value":"U","value_label":"Unchanged"},{"metric":"C","name":"Confidentiality","value":"N","value_label":"None"},{"metric":"I","name":"Integrity","value":"H","value_label":"High"},{"metric":"A","name":"Availability","value":"H","value_label":"High"}]},"cvss_v4_decoded":{"version":null,"metrics":[]},"affected":[{"vendor_slug":"zephyrproject","vendor_name":"zephyrproject","product_slug":"zephyr","product_name":"zephyr","version_start":"1.8.0","version_start_inclusive":true,"version_end":"4.4.2","version_end_inclusive":false,"cpe23_uri":"cve5:zephyrproject:zephyr:1.8.0:4.4.2"}],"exploit_refs":[],"news":[],"references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b","source_type":"PATCH","tags":["patch"]},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-h5m5-hm6j-cgpf","source_type":"VENDOR_ADVISORY","tags":["advisory"]}],"timeline":[{"type":"published","at":"2026-08-19T20:37:34.532000Z","label":"CVE published","source":null},{"type":"ssvc_changed","at":"2026-08-21T03:43:27.513265Z","label":"SSVC decision revised","source":"vulnrichment"},{"type":"ssvc_changed","at":"2026-08-21T03:43:27.513265Z","label":"SSVC decision revised","source":"vulnrichment"},{"type":"ssvc_changed","at":"2026-08-21T03:43:27.513265Z","label":"SSVC decision revised","source":"vulnrichment"}]}