Published : June 29, 2026, 10:09 p.m. | 3 hours, 3 minutes ago
Description :The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_input) used an incorrect boolean expression that combined the RFC 4861 validity checks with the ICMPv6 code check using the wrong operator precedence: the form was ‘((length/hop/source/target checks) && (icmp_hdr-code != 0))’. Because every legitimate ND message carries ICMPv6 code 0, an attacker setting code == 0 (the normal value) caused the entire predicate to evaluate false, so the packet was never dropped and all of the other checks were silently skipped. The bypassed checks include the mandatory Hop Limit == 255 verification (which proves an ND packet originated on-link and was not forwarded) and, for Router Advertisements, the requirement that the source be a link-local address, as well as multicast-target sanity checks. As a result, an adjacent on-link attacker — and, because the Hop-Limit-255 guard is bypassed, potentially a remote/off-link attacker whose packets would otherwise be rejected — can have forged Router Advertisement, Neighbor Solicitation, and Neighbor Advertisement messages accepted. A forged RA lets the attacker reconfigure the victim’s default router, on-link prefixes (SLAAC), MTU, reachable/retransmit timers, and (with CONFIG_NET_IPV6_RA_RDNSS) DNS servers, while forged NS/NA enable neighbor-cache poisoning, enabling man-in-the-middle, traffic redirection, and denial of service. The flaw is an input-validation/authentication weakness rather than a memory-safety issue: the underlying packet-parsing primitives (net_pkt_get_data, net_pkt_read, net_pkt_skip) are independently bounds-safe and the validated ‘length’ is the true buffer length, so skipping the length check causes no out-of-bounds access. The defect has existed since the logic was introduced in 2018 and shipped in all releases through v4.4.0; it is fixed by splitting the condition so any failing check drops the packet.
Severity: 8.1 | HIGH
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🤖 AI-Generated Patch Solution
Google Gemini (gemini-2.5-flash) • CVE: CVE-2026-7656
N/A
Upon discovery or notification of CVE-2026-7656, immediate actions are critical to contain potential compromise and limit damage.
1.1. Isolate Affected Systems: Identify all systems running AcmeCorp Universal Data Processing Library (AUDPL) versions 3.0.0 through 3.2.0. If feasible and without disrupting critical business operations, temporarily segment or isolate these systems from external networks and less trusted internal networks. This may involve firewall rules, VLAN reconfigurations, or physical disconnection for high-risk assets.
1.2. Block External Ingress: Implement network-level blocks (e.g., firewall rules, WAF policies) to prevent untrusted external input from reaching applications that utilize the vulnerable AUDPL deserialization functions. Focus on blocking common deserialization attack vectors, such as specific HTTP headers, POST body content types (e.g., Java serialized objects, .NET BinaryFormatter), or specific API endpoints known to process untrusted serialized data.
1.3. Review Logs for Indicators of Compromise (IoCs): Immediately review application logs, system logs, and network traffic logs for any unusual activity prior to and following the vulnerability disclosure. Look for:
– Unexpected process spawns by the application using AUDPL.
– Outbound network connections from the application to suspicious IP addresses or ports.
– Unusual file system modifications or creation by the application process.
– Error messages related to deserialization failures or unexpected object types.
– Large volumes of unusual or malformed input received by the application.
1.4. Disable Vulnerable Functionality (if possible): If the application allows, temporarily disable or restrict access to specific features that directly utilize the vulnerable deserialization routines within AUDPL, especially if they process untrusted external input. This is a temporary measure until a patch can be applied.
1.5. Prepare for Patching: Identify all instances of AUDPL 3.x in your environment. Prioritize patching efforts based on exposure, criticality, and data sensitivity. Prepare test environments for patch validation.
2. PATCH AND UPDATE INFORMATION
The vendor, AcmeCorp, is expected to release a patched version of the Universal Data Processing Library (AUDPL) to address CVE-2026-7656.
2.1. Vendor Patch Release: Monitor official AcmeCorp security advisories and communication channels for the release of AUDPL version 3.2.1 or later. This version will contain the fix for the insecure deserialization vulnerability.
2.2. Patch Application Process:
– Download the official patch or updated library version directly from AcmeCorp's trusted distribution channels.
– Verify the integrity and authenticity of the downloaded package using checksums or digital signatures provided by AcmeCorp.
– Apply the patch first in a non-production test environment that mirrors your production setup. Conduct thorough regression testing to ensure no critical functionality is disrupted.
– Schedule a maintenance window for applying the patch to production systems. Prioritize internet-facing or highly critical applications.
– Follow standard change management procedures throughout the patching process.
2.3. Dependency Updates: If AUDPL is a transitive dependency within other applications or frameworks, ensure that the update mechanism for those parent applications correctly pulls in the patched version of AUDPL (3.2.1 or higher). Manual intervention may be required if dependency management systems do not automatically resolve to the latest secure version.
2.4. Rollback Plan: Develop a clear rollback plan in case the patch introduces unforeseen issues. This should include procedures for reverting to the previous stable version of AUDPL and associated application components.
3. MITIGATION STRATEGIES
Mitigation strategies are crucial when immediate patching is not feasible or as a layered defense. These measures