EUVD-2026-63074Severity by source
AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
AV:A because Router Advertisements are link-scoped; PR:N as no credential check precedes the handler; I:H and A:H for memory integrity corruption and reliable crash; C:N as memset overwrites rather than leaks data.
Primary rating from Vendor (zephyr).
CVSS VectorVendor: zephyr
Lifecycle Timeline
3DescriptionCVE.org
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.
AnalysisAI
Memory corruption in Zephyr RTOS's IPv6 neighbor discovery stack allows any unauthenticated host on the same network link to crash or corrupt kernel memory with a single crafted ICMPv6 Router Advertisement. The handle_ra_6co() function in subsys/net/ip/ipv6_nbr.c fails to bound the 8-bit context_len field from a 6LoWPAN Context Option to the RFC 6775 maximum of 128, triggering an unsigned size_t underflow that causes memset to overwrite an unbounded region of kernel memory. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The Zephyr build must be compiled with CONFIG_NET_6LO_CONTEXT enabled - this is a non-default build-time option that must be explicitly selected; builds without it do not contain the vulnerable code path. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-assigned CVSS 8.1 score (AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H) accurately characterizes the threat profile. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the upstream patch from commit 15e838c739be637bf23fd56a5c26f2b32079551b (https://github.com/zephyrproject-rtos/zephyr/commit/15e838c739be637bf23fd56a5c26f2b32079551b), which inserts a bounds check rejecting any context_len greater than 128 before the length computation, aligning enforcement with the RFC 6775 maximum. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify and document all Zephyr RTOS deployments in your infrastructure, noting current versions and network connectivity; assess whether affected devices sit on untrusted network segments. …
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External POC / Exploit Code
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