HighCVE-2026-76505

    Cisco IOS XR Software: Improper Input Validation (CVE-2026-76505)

    Published Last modified Sources: CVE.org, BSI, Cisco PSIRT

    What is affected, what to do

    A vulnerability in the IPv4 packet processing functionality of Cisco IOS XR Software that affects Cisco ASR 9000 and 9900 Series Aggregation Services Routers as well as Cisco ASR 9902 and 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause network processor (NP) errors, resulting in a line card reset or shutdown and a denial of service (DoS) condition.  This vulnerability is due to the incorrect handling of crafted IPv4 packets that are received on an affected line card interface and processed as for-us traffic. The issue can result in an NP reset, causing traffic loss on the affected line card while it recovers.

    Update IOS XR to version 24.1.2.

    Affected
    • Cisco IOS XR Software eq 7.0.1..7.0.1
    • Cisco IOS XR Software eq 7.1.1..7.1.1
    • Cisco IOS XR Software eq 7.0.90..7.0.90
    • Cisco IOS XR Software eq 6.7.1..6.7.1
    • Cisco IOS XR Software eq 7.0.2..7.0.2
    • Cisco IOS XR Software eq 7.1.15..7.1.15
    • Cisco IOS XR Software eq 7.1.2..7.1.2
    • Cisco IOS XR Software eq 6.7.2..6.7.2
    • Cisco IOS XR Software eq 7.1.25..7.1.25
    • Cisco IOS XR Software eq 7.1.3..7.1.3
    • Cisco IOS XR Software eq 6.7.3..6.7.3
    • Cisco IOS XR Software eq 7.3.1..7.3.1
    • Cisco IOS XR Software eq 7.4.1..7.4.1
    • Cisco IOS XR Software eq 6.8.1..6.8.1
    • Cisco IOS XR Software eq 7.3.2..7.3.2
    • Cisco IOS XR Software eq 7.5.1..7.5.1
    • Cisco IOS XR Software eq 7.6.1..7.6.1
    • Cisco IOS XR Software eq 7.5.2..7.5.2
    • Cisco IOS XR Software eq 7.3.3..7.3.3
    • Cisco IOS XR Software eq 6.8.2..6.8.2
    • Cisco IOS XR Software eq 7.7.1..7.7.1
    • Cisco IOS XR Software eq 7.4.2..7.4.2
    • Cisco IOS XR Software eq 7.3.4..7.3.4
    • Cisco IOS XR Software eq 6.7.35..6.7.35
    • Cisco IOS XR Software eq 6.9.1..6.9.1
    • Cisco IOS XR Software eq 7.6.2..7.6.2
    • Cisco IOS XR Software eq 7.8.1..7.8.1
    • Cisco IOS XR Software eq 7.5.3..7.5.3
    • Cisco IOS XR Software eq 7.7.2..7.7.2
    • Cisco IOS XR Software eq 6.9.2..6.9.2
    • Cisco IOS XR Software eq 7.9.1..7.9.1
    • Cisco IOS XR Software eq 7.8.2..7.8.2
    • Cisco IOS XR Software eq 7.5.4..7.5.4
    • Cisco IOS XR Software eq 7.8.22..7.8.22
    • Cisco IOS XR Software eq 7.10.1..7.10.1
    • Cisco IOS XR Software eq 7.9.2..7.9.2
    • Cisco IOS XR Software eq 7.3.5..7.3.5
    • Cisco IOS XR Software eq 7.5.5..7.5.5
    • Cisco IOS XR Software eq 7.11.1..7.11.1
    • Cisco IOS XR Software eq 7.9.21..7.9.21
    • Cisco IOS XR Software eq 7.10.2..7.10.2
    • Cisco IOS XR Software eq 24.1.1..24.1.1
    • Cisco IOS XR Software eq 7.11.2..7.11.2
    • Cisco IOS XR Software eq 24.2.1..24.2.1
    • Cisco IOS XR Software eq 24.1.2..24.1.2
    • Cisco IOS XR Software eq 24.3.1..24.3.1
    • Cisco IOS XR Software eq 24.4.1..24.4.1
    • Cisco IOS XR Software eq 24.2.2..24.2.2
    • Cisco IOS XR Software eq 7.8.23..7.8.23
    • Cisco IOS XR Software eq 7.11.21..7.11.21
    • Cisco IOS XR Software eq 24.3.2..24.3.2
    • Cisco IOS XR Software eq 24.3.20..24.3.20
    • Cisco IOS XR Software eq 24.3.30..24.3.30

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    Metrics

    7.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org, BSI, Cisco PSIRT

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 40.3

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    80.52 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.5 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    40.3
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-20

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A vulnerability in the IPv4 packet processing functionality of Cisco IOS XR Software that affects Cisco ASR 9000 and 9900 Series Aggregation Services Routers as well as Cisco ASR 9902 and 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause network processor (NP) errors, resulting in a line card reset or shutdown and a denial of service (DoS) condition.&nbsp; This vulnerability is due to the incorrect handling of crafted IPv4 packets that are received on an affected line card interface and processed as for-us traffic. The issue can result in an NP reset, causing traffic loss on the affected line card while it recovers. Under repeated reset conditions, the network processor may enter a persistent shutdown state, in which case an explicit line card reload may be required to restore traffic. The vulnerability is within the IPv4 packet-processing path. Transit IPv4 traffic does not trigger this issue and IPv6 traffic cannot trigger it.

    Source: NVD (NIST), BSI CSAF, BSI WID Portal, CVE.org (MITRE), cvelistv5, cisco_csaf

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    CiscoCisco IOS XR Software
    • 7.1.25
    • 7.7.2
    • 24.4.1
    • 7.5.4
    • 7.1.15
    • 7.0.1
    • 7.0.90
    • 6.7.3
    • 7.9.21
    • 7.3.2
    • 7.8.2
    • 7.5.1
    • 7.10.1
    • 7.4.2
    • 7.1.3
    • 7.3.3
    • 7.3.5
    • 7.3.4
    • 7.5.2
    • 6.7.1
    • 24.3.20
    • 6.8.1
    • 24.1.1
    • 7.4.1
    • 24.3.30
    • 6.9.2
    • 24.2.1
    • 7.8.22
    • 6.9.1
    • 24.2.2
    • 6.7.35
    • 7.9.1
    • 7.11.1
    • 7.7.1
    • 7.11.21
    • 7.3.1
    • 7.11.2
    • 7.8.23
    • 7.0.2
    • 6.7.2
    • 7.5.5
    • 24.3.2
    • 24.1.2
    • 7.1.2
    • 7.10.2
    • 24.3.1
    • 7.5.3
    • 7.8.1
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    Vendors and products

    Weakness classes (CWE)

    • CWE-20Improper Input Validation

      Class

      The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

      Entry at MITRE CWE-20

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-76505","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-21T17:11:38.778800Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Linked advisories

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    <a href="https://intel.neosec.eu/en/cve/CVE-2026-76505"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-76505.svg?lang=en" alt="CVE-2026-76505 – NEOSEC Intel" height="20"></a>