CVE-2026-76464

Executive Summary

CVE-2026-76464 is a high-severity (CVSS 9.6) vulnerability class affecting Cisco networking products, stemming from buffer management issues grouped under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The advisory describes multiple internally discovered vulnerabilities disclosed as part of a Cisco proactive security review and hardening release; no affected product list, version range, or specific component is named in the available data. Impact at this severity is potentially total: scope-changed, high confidentiality, integrity, and availability impact, exploitable from an adjacent network position without authentication or user interaction.

Technical Analysis

CWE-119 is the parent classification for improper restriction of operations within the bounds of a memory buffer. This category encompasses classic memory-corruption primitives — out-of-bounds reads and writes, buffer overflows, and memory-safety defects that can result in crashes, memory disclosure, or arbitrary code execution depending on the exposed code path.

The CVE description states explicitly that this identifier tracks multiple internally discovered vulnerabilities "related to buffer management issues." This is a grouped CVE covering more than one defect rather than a single localized flaw. The unifying technical theme is memory-buffer handling inside Cisco networking software.

Key inference constraints from the data provided:

• No specific function, library, process, protocol, port, or file path is named in the NVD description or CNA title. Any claim of a specific parsing routine, CLI handler, or daemon would be fabrication and is deliberately omitted here.
• The CVSS vector AV:A (Adjacent) means the attack surface is reachable from an adjacent network segment — not the public internet directly, but a logically or physically adjacent network position. In networking-device contexts this typically corresponds to a directly connected or same-L2-domain attacker, or an attacker who has already gained a foothold on an adjacent segment.
• PR:N indicates no prior authentication is required.
• UI:N indicates no user interaction is required.
• S:C (Scope Changed) indicates the vulnerable component's exploitation can affect resources beyond its original security scope — significant for network infrastructure where compromise of one process or plane can affect the whole device.
• AC:L indicates the attack is straightforward once the attacker has adjacent access; no special-conditions race or complex timing is implied.

Because the affected products are not enumerated, the concrete attack surface (which protocol parser, management interface, or data plane path is reachable from an adjacent segment) cannot be specified from the supplied data. This is a material intelligence gap: operators must identify affected Cisco assets in their own inventory and consult Cisco's security advisory for the definitive product and version matrix.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template is available for this CVE. The attack chain below is described at the vulnerability-class level and inferred from the CVSS vector and CWE classification. Specific implementation details are not fabricated.

1. Reconnaissance / target identification. An adversary with a presence on a network segment adjacent to Cisco networking equipment identifies candidate targets — devices reachable from that position (for example on the same Layer-2 domain or directly connected segment). No authentication is required for the eventual attempt, so the primary reconnaissance goal is reachability and identification of Cisco devices and the services/ports they expose to the adjacent network.

2. Trigger of the flaw class. The attacker delivers crafted input to a reachable buffer-handling code path. Consistent with CWE-119 and the description's "buffer management issues," the malformed input causes the software to operate outside the intended bounds of a memory buffer. Because the exact interface is undisclosed, the delivery vector could be any memory-handling path exposed by the affected Cisco software to an adjacent attacker — the report does not assert a specific protocol or port. No credentials are needed (PR:N) and no user action is required (UI:N).

3. Payload / execution. At the vulnerability-class level, improper buffer bounds handling can yield out-of-bounds reads (information disclosure) or out-of-bounds writes (memory corruption). The CVSS C:H/I:H/A:H and S:C subscores are consistent with a flaw whose consequences can extend to disclosure, modification, and loss of availability across the affected device's scope. Whether the specific defect yields reliable code execution, device crash/restart, or data disclosure cannot be determined from the available data.

4. Post-exploitation impact. Given Scope Changed and high impact across all three security objectives, a successful exploit of a networking device can compromise the confidentiality of data processed by the device, the integrity of its configuration and forwarding behavior, and its availability. On network infrastructure, such access can serve as a pivot point into adjacent segments and as a position from which traffic or configuration can be manipulated — but this report does not assert specific post-exploitation tooling or lateral-movement techniques beyond what the CVSS subscores imply.

No threat actor attribution, exploit-in-the-wild evidence, or campaign reporting is present in the supplied data.

Impact Assessment

• Severity: CVSS 3.1 base score 9.6 — Critical.
• Exploitability: Adjacent attack vector (AV:A), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N). This is a highly favorable exploitation profile for an attacker already positioned on an adjacent network segment.
• Impact subscores: Confidentiality High, Integrity High, Availability High — a full-impact profile across all three objectives.
• Scope: S:C — Scope Changed. Exploitation of the vulnerable component can impact resources beyond its original authorization scope, which raises the blast radius relative to a same-scope flaw.
• Affected systems: Cisco networking products are the stated product family, but no specific product list or version range is disclosed in the available data. Organizations must map affected assets against Cisco's advisory.
• Blast radius: Networking devices sit at network chokepoints. A fully impactful compromise at a chokepoint can affect the confidentiality, integrity, and availability of traffic and configuration traversing it, and can create a pivot into segments beyond the victim device.
• EPSS: Not yet scored by FIRST.org. No probability estimate is asserted here.
• Known exploitation: CISA KEV: NO. No public PoC, no exploit code, no Nuclei template.

Detection Guidance

Detection content below is generic to memory-buffer corruption and adjacent-anomaly activity, because no protocol, port, or interface is disclosed for this CVE. Rules should be tuned to the specific Cisco advisory once product details are available.

Sigma Rule

title: Cisco Networking Device Buffer Corruption - Crash/Reboot or Fault Indicators
id: 3f9a1c2e-7646-4b1a-9d2e-000000764640
status: experimental
description: Detects anomalous fault, crash, or memory-error events on Cisco networking devices consistent with CWE-119 buffer management exploitation (CVE-2026-76464). Tune syslog source to affected product lines.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76464
author: valtersit.com
date: 2026/01/01
logsource:
  product: cisco
  service: syslog
detection:
  selection_fault:
    - '%' # placeholder prefix; tune per platform
  keywords:
    - 'buffer'
    - 'out of bounds'
    - 'memory allocation'
    - 'malloc failure'
    - 'crash'
    - 'unexpected reload'
    - 'critical fault'
  condition: keywords
falsepositives:
  - Routine device reboots and maintenance events
  - Legitimate high-memory conditions
level: high
tags:
  - attack.t1190
  - cve.2026.76464

YARA Rule

rule CVE_2026_76464_Cisco_Buffer_Bounds_Indicator
{
    meta:
        description = "Generic indicator rule for CWE-119 buffer-bound handling anomalies in Cisco networking firmware images compiled with known unsafe copy patterns. Advisory lists no specific function names, so this matches common unsafe-buffer idioms only."
        cve = "CVE-2026-76464"
        cwe = "CWE-119"
        author = "valtersit.com"
        date = "2026-01-01"

    strings:
        $a = "BUFFER OVERFLOW" ascii nocase
        $b = "buffer overflow" ascii nocase
        $c = "out of bounds" ascii nocase
        $d = "bounds check" ascii nocase
        $e = "strcpy" ascii
        $f = "memcpy" ascii
        $g = "Cisco" ascii

    condition:
        filesize < 200MB and
        $g and
        2 of ($a, $b, $c, $d, $e, $f)
}

Suricata IDS Rule

alert tcp any any -> $HOME_NET any (msg:"CVE-2026-76464 Possible Cisco Buffer Management Exploitation Attempt (adjacent)"; flow:to_server,established; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-admin; reference:cve,2026-76464; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-76464; metadata:created_at 2026_01_01, cve CVE_2026_76464; sid:202676464; rev:1;)

alert udp any any -> $HOME_NET any (msg:"CVE-2026-76464 Possible Cisco Buffer Management Exploitation Attempt (udp, adjacent)"; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-admin; reference:cve,2026-76464; sid:202676465; rev:1;)

Note: no protocol or port is disclosed for this CVE; these rules are rate/anomaly heuristics and must be constrained to the actual affected service once Cisco confirms it.

Elastic Detection

sequence by host.hostname with maxspan=2m
  [ network where network.direction == "inbound" and source.ip != null ]
  [ log where (event.provider == "Cisco" or host.hostname : "cisco*")
      and (message : "buffer" or message : "out of bounds" or message : "unexpected reload"
           or message : "critical fault" or message : "memory allocation") ]

Splunk SPL Query

index=cisco OR index=network
| eval msg=lower(_raw)
| where match(msg,"buffer|out of bounds|memory allocation|unexpected reload|critical fault|segfault")
| stats count min(_time) as first_seen max(_time) as last_seen values(host) as hosts by src_ip, msg
| where count >= 5
| sort - count

Wazuh OSSEC Rule

<group name="cisco,cve-2026-76464,">
  <rule id="100764" level="12">
    <decoded_as>json</decoded_as>
    <match>buffer|out of bounds|memory allocation|unexpected reload|critical fault</match>
    <description>CVE-2026-76464: Possible Cisco buffer management exploitation - memory/buffer anomaly on networking device</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No patch source, version, or advisory ID is available in the tracked data. The only reference to a fix is the Cisco statement describing an internal review resulting in a "software hardening release"; no version, advisory identifier, or download location is disclosed here.

1. Immediate mitigations

   • Treat this as unpatched until Cisco confirms otherwise. Locate and read the authoritative Cisco security advisory for CVE-2026-76464 to obtain the affected product/version matrix and fixed release.
   • Reduce adjacent attack surface: restrict which systems can reach Cisco networking devices from adjacent segments; apply segmentation and ACLs so only trusted management/adjacent hosts are permitted.
   • Harden management access: restrict management interfaces to out-of-band or trusted management networks, disable unnecessary services exposed to adjacent segments, and enforce strong authentication.
   • Monitor for device crashes, reboots, or memory faults that could indicate triggering of a buffer management defect.

2. Patch / upgrade steps

   • No patch version is available in the tracked data. Once Cisco publishes the advisory, inventory affected devices, identify the fixed software release, and follow Cisco's upgrade guidance and release notes.
   • Stage upgrades in a maintenance window given the possibility of availability impact during the process.

3. Long-term hardening

   • Adopt continuous vulnerability management for network infrastructure, including tracking Cisco advisories and CVE-2026-76464 specifically.
   • Enforce network segmentation and least-privilege access between adjacent segments and infrastructure devices.
   • Deploy the detection rules above (tuned to affected product lines) to gain early warning of anomaly activity.
   • Maintain an asset inventory with accurate product/version data so that this — and future — Cisco advisories can be mapped to assets quickly.

References

• NVD — CVE-2026-76464: https://nvd.nist.gov/vuln/detail/CVE-2026-76464
• CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer: https://cwe.mitre.org/data/definitions/119.html
• Cisco Security Advisories portal: https://sec.cloudapps.cisco.com/security/center/publicationListing.x
• FIRST EPSS (no score available as of this report): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-76464 not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No exploit-in-the-wild evidence, public PoC, or threat actor campaign attribution is present in the available data for CVE-2026-76464.