🔥 CyberForge CVE of the Day #072 🚨 CVE-2026-76471 — Cisco NX-OS: a critical management-interface vulnerability Cisco reports insufficient NX-API input validation that can allow root-level code execution on affected Nexus switches, or cause process failures that may reload the device and interrupt service. For Nexus, the conditions are an affected release and NX-API enabled; prior credentials and user interaction are not required. UCS 6300 has a separate route requiring valid low-privileged credentials through UCS Manager XML API. 🗓️ Research snapshot: 8 October 2026, 09:28 UTC. Cisco advisory v1.0: 7 October, 16:00 GMT. CVE publication: 7 October, 16:15 UTC. The status statements below retain that research cutoff. 🎯 THE QUICK HIT Who needs to review this? Owners of Nexus 3000, Nexus 9000 standalone NX-OS, and UCS 6300 Fabric Interconnects. For Nexus, confirm model, running release and effective NX-API state. The feature is disabled by default, but deployed configuration matters. Why separate UCS? Its route requires valid low-privileged credentials. UCS Manager XML API is enabled by default and cannot be disabled without loss of functionality. Cisco assigns UCS 6300 a High security impact rating; keep this condition beside the advisory’s overall 9.8 Critical score. What resolves it? Supported fixed software. For four Nexus 9000 examples checked against this individual advisory, Cisco returned: 10.3(9) → 10.3(10) 10.4(7) → 10.4(8) 10.5(5) → 10.5(6) 10.6(3) → 10.6(4) These are specific query results, not universal repair versions for all models, trains or Nexus 3000. For UCS 6300 4.3: UCS Manager Managed: 4.3(6j) Intersight Managed: 4.3(6.260049) For 4.2 and earlier, migrate to a fixed release. Retain the management mode beside the version. What while scheduling? Cisco documents temporary Live Protect shield lp00074 for supported Nexus hardware on 10.6(3). Confirm compatibility and effective policy mode. Monitoring records observations. Enforcement blocks or mitigates within supported scope. Package presence alone does not establish enforcement, and fixed software remains the remediation. Where should the SOC start? Confirm the device and management path, preserve retained evidence, and correlate unusual API activity with device events and independently supported changes. An error, shield event or reload is a lead requiring context. It does not alone prove successful unauthorised code execution. 🔑 KEY DETAILS CVE: CVE-2026-76471. Vendor: Cisco. Advisory: cisco-sa-napi-rce-r2shwu2j, version 1.0 Final. Cisco CNA severity: CVSS v3.1 9.8 Critical. Base vector: CVSS:3.1/AV/AC/PR/UI/S/C/I/A. Weakness: CWE-122 — Heap-based Buffer Overflow. Nexus condition: affected release with NX-API enabled. Nexus access requirement: network access to the interface; no prior credentials or user interaction. UCS 6300 condition: valid low-privileged credentials through UCS Manager XML API. UCS 6300 vendor security impact rating: High. Documented outcomes: root-level code execution, or process failures that may cause a reload and denial of service. Permanent remediation: supported fixed software. Temporary protection: compatible Live Protect deployment, with effective policy mode verified. No separate UCS CVSS vector was supplied in the reviewed advisory. No CVSS v4.0 metric was present in the reviewed CNA or NVD material. At the research cutoff, NVD marked the record Received and attributed its v3.1 metric to Cisco PSIRT. An independent NIST severity assessment was not present. The retrieved CISA KEV catalogue was version 2026.10.04, with 1,734 entries, and contained no exact match for this CVE. That catalogue predates the disclosure. FIRST returned no EPSS estimate for this CVE. The score, percentile and score date were unavailable. An unavailable estimate must not be treated as a zero score. Cisco PSIRT’s dated advisory said it was not aware of public announcements or malicious use. Cisco attributed discovery to internal security testing. 🧠 THE ISSUE IN PLAIN TERMS A management interface must keep incoming information within the limits its implementation can safely process. Cisco describes insufficient NX-API input validation; the CNA classifies the weakness as a heap-based buffer overflow. Specially formed input can lead to unsafe memory handling, with root-level execution or disruptive process failure. A normal API login prompt does not remove the published Nexus condition. UCS 6300 has its own credential requirement and XML API context. The reviewed material does not identify the exact input field, complete request shape or detailed execution sequence. It does not support a universal content signature inferred from the description. The documented capability also does not establish an organisation’s outcome. Persistence, configuration theft or subsequent access require independent evidence. A reload has several possible causes. The useful comparison ties management activity, device events and supporting records to the same asset and time window. 📦 WHICH DEPLOYMENTS BELONG IN SCOPE? Ask three separate questions. 1 — Product and mode The affected scope is Nexus 3000, Nexus 9000 standalone NX-OS, or UCS 6300. Cisco excludes Nexus 9000 ACI, Nexus 7000, MDS 9000 and UCS 6400/6500/6600 among confirmed unaffected products. Match the actual family and mode rather than relying on a similar vendor or software label. 2 — Running release The CNA provides explicit affected-version entries. An unlisted release is not automatically fixed, and train-specific notation should not be compared as ordinary decimal numbers. Use Cisco’s checker for the actual Nexus platform/release and retain the individual advisory selected. Choose supported software and an approved upgrade path. 3 — Management access Establish Nexus NX-API state and listeners. For UCS 6300, establish XML API identities and credential access. The checker does not account for feature state. Software applicability, effective interface state and reachability each need evidence. Record stable asset identity, model, operating/management mode, running release, owner and management path. Include relevant peers and direct routes; a restricted frontend does not settle every access path. 🕰️ ESTABLISH THE EXPOSURE WINDOW Disclosure is not proof that exposure began on the publication date. Use retained release history, configuration archives, approved changes and management records to bound when the relevant conditions were present. Keep supported observations, retention and gaps. Disabled now does not reconstruct past state. Enforcement now does not prove earlier protection. A fixed release now does not settle earlier unexplained activity. Preserve original device/collector timestamps and offsets, then build a UTC timeline with stated clock uncertainty. Join stable device and module identity where available. A reused, shared or translated management address can be an unreliable case key. 🔎 THE SOC TRAIL — SIX CHECKS FOR THE CASE 01 — SCOPE THE DEVICE AND MANAGEMENT PATH Action: confirm model, mode, running software and interface state with the network owner. Where: approved inventory, supported management views, configuration history and existing policy/flow records. Signal and correlation: affected Nexus release + NX-API enabled + reachable listener. For UCS 6300, add the XML API identity and credential condition. Save the actual Cisco platform/release selection. Normal explanation: orchestration, monitoring and backups legitimately use APIs. Compare source, identity and schedule. Escalation: unexpected reachability or unresolved state needs an owner and deadline. Applicable devices reachable beyond their intended management boundary need urgent repair planning. 02 — PRESERVE THE AVAILABLE EVIDENCE Action: preserve the useful interval before approved restarts or cleanup where practicable. Where: existing syslog, retained API errors, reset history, crash-artifact inventory and management/identity records. Use supported owner or Cisco TAC collection procedures. Keep originals restricted and record device, release, collection time, retention and integrity details. Use redacted working copies. Correlation: align errors, resets and policy events with the same device and management window. A crash artifact still needs analysis. Normal explanation: upgrades, software/hardware faults, resource pressure and long-running management operations can interrupt service. Escalation: unexplained resets with unexpected API activity or integrity changes warrant closer review. Preserve context before assigning cause. 03 — REVIEW API AND SHIELD OBSERVATIONS Action: review unexpected clients, unusual rates, errors and timeouts. Where: available management access/flow records, appliance errors and NXSecure observations on supported deployments. Confirm the listener, normal automation and collection health. Cisco documents a critical-threat event for shield lp00074, with policy name cve-nxapi-rce. Join device, policy, effective mode and time to independent traffic or state evidence. A policy event deserves prompt review but does not automatically prove successful execution. Monitoring does not block; enforcement is temporary protection within supported scope. Normal explanation and limit: generic errors can reflect ordinary operational problems. Bounded history, zero hits or a quiet collector do not establish full past coverage. Escalation: review a credible CVE-related policy observation even without a reload. Record deployment time, mode changes and retained coverage. 04 — CORRELATE THE DEVICE OUTCOME Action: connect management activity → device event → resulting change only where records support each step. Where: configuration archives, approved changes, authentication/accounting records, syslog, reset context and independent network observations. Signals: unexplained configuration changes, unexpected account activity, unusual management sessions or device-originated traffic. These are behavioural leads requiring corroboration. Prefer stable asset identity, available session/request identifiers and a stated time tolerance. Root-level activity need not create a new account or visible configuration change. Normal explanation: deployment, backups, monitoring, failover and clock differences can resemble a suspicious sequence. Escalation: API or shield observations aligned with unexplained integrity/identity changes deserve IR review. Record the normal explanations considered and their supporting evidence. 05 — REMEDIATE WITH THE OWNER Action: choose supported fixed software for the actual model, train and management mode; agree maintenance and failover. Where: the individual advisory, platform-specific checker, compatibility guidance and approved change record. Retain asset, previous release, chosen fix, deployment time and post-change running state. Other applicable advisories can inform release selection without changing this CVE’s prerequisites. Approved management restrictions can reduce exposure while scheduling. Changes to Nexus NX-API require a dependency check. Cisco says no workaround addresses the vulnerability. UCS XML API has the explicit functionality-loss caveat. For temporary lp00074, verify listed hardware, 10.6(3) and operational requirements; do not extend its scope to all Nexus or UCS. 06 — VERIFY RUNNING STATE AND RETAIN GAPS Action: confirm running software on each applicable asset/peer, then review API state, intended reachability and collection health. Where: supported device views, saved Cisco results and approved network-policy evidence. A staged image or completed ticket is insufficient. For temporary protection, verify healthy NXSecure and effective Current mode. An original setting or package name may not describe the mode in effect. Keep installation/mode-change times and coverage. Cisco says lp00074 becomes N/A after an upgrade to 10.6(4) or higher. Assess that alongside the running fixed release; N/A is not enforcing. Handover: assign missing history, API records, policy state or reset evidence as owned gaps. Close repair with running-release evidence and the historical review with a bounded conclusion. 🧭 THE ANALYST HANDOVER Pass stable asset/model/mode, running release, API state, management path and UTC window with clock uncertainty. Add saved Cisco results, source/retention/integrity details, shield deployment and effective mode, observed events, approved changes, correlation confidence and remaining gaps with owners. Keep four outcomes separate: No finding in the reviewed sources/window. Insufficient coverage. Suspicious activity requiring review. Corroborated unauthorised activity or compromise. Current remediation and historical investigation answer different questions. Give the next shift enough evidence to continue without rebuilding the case. 🔬 INDICATORS AND EVIDENCE LIMITS Verified vocabulary includes lp00074, cve-nxapi-rce and its Cisco NXSecure alert context. These identify a defensive policy, not attacker infrastructure. Unexpected clients, errors, resets and unexplained changes are leads when tied to the same asset/window. No malicious address, domain, hash, exact content signature or named actor was established in the reviewed primary material. No independently verified public exploit was established by the bounded review. This does not exclude private capability or later publication. Preserve raw observations when normalising collector formats, including original device identity, mode and timestamp. 🧰 PRACTICAL OWNER CHECKS A — Confirm applicability Obtain the supported model/running-release view, Nexus NX-API state and actual listener configuration from the owner. For UCS 6300, confirm management mode, software and XML API identities. Compare the actual platform/release with Cisco guidance and mark missing information unresolved. Version alone does not establish reachability. Feature state alone does not establish vulnerability. Current state does not reconstruct historical exposure. B — Establish the device-event context Review retained logs, reset history and crash-artifact inventory through supported management facilities. Keep time, reason, module and release context where available, plus retention, truncation and permission limits. Support bundles and crash exports may contain sensitive information or add collection load; agree their handling with the owner/TAC. A reset entry cannot independently attribute its cause to this CVE. C — Verify temporary policy state Where lp00074 is supported and deployed, confirm NXSecure health, package identity and effective Current mode. Record observation time and overrides. Original settings can differ from the current mode. Monitoring observes without blocking. Enforcement supplies temporary protection within scope. N/A or unavailable output needs interpretation alongside release and compatibility. A hit counter is not a compromise counter. Zero does not establish coverage of the complete exposure window. 🩹 REMEDIATION AND ACCEPTANCE EVIDENCE For Nexus, retain the exact platform-and-release selection, supported fixed software choice and running release after the approved change. For UCS 6300, preserve the management mode beside the repair version: 4.3(6j) for UCS Manager Managed, or 4.3(6.260049) for Intersight Managed. Older 4.2-and-earlier deployments require migration to a fixed release. For temporary lp00074 protection, retain compatible hardware and release, package identity, healthy NXSecure state, effective mode and collection coverage. Keep the fixed-software maintenance plan in place. Consult Cisco’s upgrade and downgrade guidance before changing releases. Preserve investigation records before operational cleanup where possible. Avoid unnecessary service restarts, logging changes or replay of suspect traffic during routine triage. If independent evidence indicates integrity loss or unauthorised activity, involve incident response and Cisco TAC. Review relevant configurations and identities with the appropriate owners. Installing fixed software addresses the vulnerable implementation. It does not certify historical integrity or settle the meaning of earlier unexplained events. 🧾 WHAT IS CONFIRMED, AND WHAT REMAINS ANALYSIS? Vendor/CNA facts: platform conditions, input-validation weakness, CWE-122, documented outcomes, exact vector, fixed-software guidance and temporary shield. Dated assessments: Cisco PSIRT awareness, retrieved KEV status and unavailable EPSS. CISA ADP records Exploitation none, Automatable yes and Technical Impact total, timestamped 7 October 00:00 UTC. This is an assessment snapshot, not continuing proof about every environment. Forge analysis: prioritisation, preservation, behavioural review, correlation and acceptance criteria. Unknowns: detailed trigger, private/later activity, real exposure history and organisational integrity. The CNA lists defect CSCwu46202; the advisory lists CSCwu46199/CSCwu58579 and the shield references CSCwu46199. Their complete mapping was not established. 🔥 CYBERFORGE VERDICT An affected reachable Nexus NX-API service needs urgent attention: Cisco describes root-level execution without prior credentials. Keep UCS 6300’s credential condition and High rating visible so owners assess the correct path. Choose supported fixed software, limit the shield to its temporary documented scope and verify running state. The strongest SOC trail joins management access, device/policy observations and independently supported changes. Check approved work and preserve the evidence. No findings does not prove a clean system. KEV absence and unavailable EPSS do not settle exposure or integrity. An owned inventory, a clear evidence window and verified upgrade give the next shift solid ground. 🔗 PRIMARY SOURCES Cisco advisory, platform prerequisites and UCS fixes: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-napi-rce-r2shwu2j Cisco Software Checker — query your exact platform/release: https://sec.cloudapps.cisco.com/security/center/softwarechecker.x CVE record / Cisco CNA: https://www.cve.org/CVERecord?id=CVE-2026-76471 NVD record: https://nvd.nist.gov/vuln/detail/CVE-2026-76471 Cisco lp00074 scope, policy and alert examples: https://www.cisco.com/c/en/us/td/docs/dcn/nx-os/nexus9000/106x/release-notes/nxos-live-protect-shield-lp00074.html Cisco NX-API troubleshooting: https://www.cisco.com/c/en/us/td/docs/dcn/nx-os/nexus9000/106x/configuration/troubleshooting/cisco-nexus-9000-series-nx-os-troubleshooting-guide-106x/m-troubleshooting-nx-api.html CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog FIRST EPSS exact-ID lookup: https://api.first.org/data/v1/epss?cve=CVE-2026-76471 #CyberForge #CVEOfTheDay #CVE202676471 #Cisco #NXOS #BlueTeam #SOC #IncidentResponse
