CVE-2026-10657: bounds in zephyrproject zephyr
Zephyr's DNS resolver detects mDNS (.local) queries in dns_resolve_name_internal() (subsys/net/lib/dns/resolve.c) with memcmp(strrchr(query, '.'), ".local", 7), which always reads a fixed 7 bytes from the suffix pointer. When the resolved hostname's final label is shorter than 7 bytes (e.g. names ending in .org, .com, .net, .io, or a trailing dot), the comparison reads 1-2 bytes past the string's NUL terminator. The hostname (query) is the caller-supplied name passed through the standard getaddrinfo()/dns_get_addr_info()/dns_resolve_name() path and is influenceable by operators or remote inputs (server names from configuration, parsed URLs, or app-facing interfaces). On a tightly-sized buffer with no slack (for example a userspace getaddrinfo call where the hostname is copied with k_usermode_string_alloc_copy to exactly strlen+1 bytes), the over-read crosses the allocation boundary; if that boundary is unmapped (guard page, memory-domain boundary under MPU, or an address sanitizer) the over-read faults, causing a denial of service. The over-read bytes are never returned, so there is no information disclosure. The flaw is compiled only when CONFIG_MDNS_RESOLVER is enabled, exists since v1.10.0, and is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp(ptr, ".local").
AI Analysis
Technical Summary
Zephyr's DNS resolver function dns_resolve_name_internal() uses memcmp with a fixed length of 7 bytes to detect mDNS queries ending in ".local". When the hostname's final label is shorter than 7 bytes, this causes a read beyond the string's NUL terminator, potentially crossing allocation boundaries. If the memory beyond the buffer is unmapped (e.g., guard pages or MPU boundaries), this results in a denial of service due to a fault. The vulnerability is present since version 1.10.0 and only when CONFIG_MDNS_RESOLVER is enabled. It is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp to prevent out-of-bounds reads.
Potential Impact
The vulnerability can cause a denial of service by triggering a fault when the out-of-bounds read crosses an unmapped memory boundary. There is no impact on confidentiality or integrity as the over-read bytes are never returned or exposed. The attack vector is network-based with no privileges required, but the attack complexity is high due to the need for specific memory conditions.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The vulnerability is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp in the DNS resolver code. Users should verify if their Zephyr version includes this fix or upgrade to a version where the fix is applied. If upgrading is not immediately possible, disabling CONFIG_MDNS_RESOLVER can mitigate the issue by avoiding the vulnerable code path.
CVE-2026-10657: bounds in zephyrproject zephyr
Description
Zephyr's DNS resolver detects mDNS (.local) queries in dns_resolve_name_internal() (subsys/net/lib/dns/resolve.c) with memcmp(strrchr(query, '.'), ".local", 7), which always reads a fixed 7 bytes from the suffix pointer. When the resolved hostname's final label is shorter than 7 bytes (e.g. names ending in .org, .com, .net, .io, or a trailing dot), the comparison reads 1-2 bytes past the string's NUL terminator. The hostname (query) is the caller-supplied name passed through the standard getaddrinfo()/dns_get_addr_info()/dns_resolve_name() path and is influenceable by operators or remote inputs (server names from configuration, parsed URLs, or app-facing interfaces). On a tightly-sized buffer with no slack (for example a userspace getaddrinfo call where the hostname is copied with k_usermode_string_alloc_copy to exactly strlen+1 bytes), the over-read crosses the allocation boundary; if that boundary is unmapped (guard page, memory-domain boundary under MPU, or an address sanitizer) the over-read faults, causing a denial of service. The over-read bytes are never returned, so there is no information disclosure. The flaw is compiled only when CONFIG_MDNS_RESOLVER is enabled, exists since v1.10.0, and is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp(ptr, ".local").
CVSS v3.1
Score 3.7low
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Zephyr's DNS resolver function dns_resolve_name_internal() uses memcmp with a fixed length of 7 bytes to detect mDNS queries ending in ".local". When the hostname's final label is shorter than 7 bytes, this causes a read beyond the string's NUL terminator, potentially crossing allocation boundaries. If the memory beyond the buffer is unmapped (e.g., guard pages or MPU boundaries), this results in a denial of service due to a fault. The vulnerability is present since version 1.10.0 and only when CONFIG_MDNS_RESOLVER is enabled. It is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp to prevent out-of-bounds reads.
Potential Impact
The vulnerability can cause a denial of service by triggering a fault when the out-of-bounds read crosses an unmapped memory boundary. There is no impact on confidentiality or integrity as the over-read bytes are never returned or exposed. The attack vector is network-based with no privileges required, but the attack complexity is high due to the need for specific memory conditions.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The vulnerability is fixed by replacing the fixed-length memcmp with a NUL-safe strcmp in the DNS resolver code. Users should verify if their Zephyr version includes this fix or upgrade to a version where the fix is applied. If upgrading is not immediately possible, disabling CONFIG_MDNS_RESOLVER can mitigate the issue by avoiding the vulnerable code path.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- zephyr
- Date Reserved
- 2026-06-02T15:24:32.170Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4ae01927e9c79719f45653
Added to database: 07/05/2026, 22:52:09 UTC
Last enriched: 07/20/2026, 19:09:59 UTC
Last updated: 08/19/2026, 22:52:10 UTC
Views: 156
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