CriticalCVE-2025-20281

    Cisco ISE API Unauthenticated Remote Code Execution Vulnerability (CVE-2025-20281)

    Published In CISA KEV since Sources: pwn.watch, CVE.org, CERT-EU, SingCERT

    What is affected, what to do

    An unauthenticated, remote attacker can perform remote code execution (RCE) as root on Cisco ISE and Cisco ISE-PIC devices due to insufficient validation of user-supplied input in a specific API. This vulnerability is actively exploited, as indicated by its inclusion in the CISA KEV catalog. All versions of Cisco Identity Services Engine are affected. Immediate patching to the latest version is critical to mitigate this high-severity vulnerability.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Cisco Identity Services Engine Software eq 3.3.0..3.3.0
    • Cisco Identity Services Engine Software eq 3.3 Patch 2..3.3 Patch 2
    • Cisco Identity Services Engine Software eq 3.3 Patch 1..3.3 Patch 1
    • Cisco Identity Services Engine Software eq 3.3 Patch 3..3.3 Patch 3
    • Cisco Identity Services Engine Software eq 3.4.0..3.4.0
    • Cisco Identity Services Engine Software eq 3.3 Patch 4..3.3 Patch 4
    • Cisco Identity Services Engine Software eq 3.4 Patch 1..3.4 Patch 1
    • Cisco Identity Services Engine Software eq 3.3 Patch 5..3.3 Patch 5
    • Cisco Identity Services Engine Software eq 3.3 Patch 6..3.3 Patch 6

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    10.0

    Priority

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

    Source: NVD, CVSS v3

    10.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, CVE.org, CERT-EU, SingCERT

    97.6 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.90

    Show all metrics
    Severity
    Critical
    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
    239.46 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
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    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
    10.0 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
    10.0
    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
    97.6 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.90
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    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
    Actively exploited
    Published
    In CISA KEV since

    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
    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-74

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction, yields root directly and has scope-changing impact. It sits among the CVEs most likely to be exploited, and public technical write-ups have lowered the bar for attackers considerably. ISE is a high-value target as the central NAC/AAA authority: owning it hands an attacker access policy, shared secrets and AD integration, making it a launchpad for lateral movement even though CISA reports no ransomware use. Treat every affected ISE node as critical with a remediation window measured in hours. Where the API was reachable from outside the management network, assume possible compromise and run a forensic review alongside patching.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Enumerate every Cisco ISE and ISE-PIC node (PAN, MnT, PSN) with its exact version (show version or Administration > System > Deployment). Per the context, affected releases are 3.3.0, 3.3 Patch 1–5, 3.4.0 and 3.4 Patch 1. 3.2 and earlier are not listed here, but verify against the vendor advisory.
      • Patch: A fix is available from Cisco — look up the fixed release in the Cisco Security Advisory for CVE-2025-20281. Use only the patch releases the advisory marks as fully remediated, not interim hotfixes. Roll out to the PAN first, then MnT, then PSNs.
      • Cut exposure now: Block the ISE admin GUI and API interfaces (HTTPS/TCP 443, ERS API typically TCP 9060) from the internet and from user VLANs. Allow access only from a dedicated management network or jump hosts.
      • Compromise assessment before patching: Collect a support bundle and logs before rebooting or upgrading. Unauthenticated root RCE means patching will not evict an attacker who is already in.
      • Rotate secrets on any indicator: ISE is your AAA core. Rotate RADIUS/TACACS+ shared secrets, the AD join account, admin passwords, pxGrid and system certificates, and ERS/OpenAPI accounts.
      • Regulatory clock: If compromise is confirmed, start the NIS2 24-hour early-warning notification to BSI or your national CSIRT.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Put an ACL or firewall in front of all ISE nodes. Permit RADIUS (UDP 1812/1813, 1645/1646) and TACACS+ (TCP 49) only from network devices. Permit TCP 443, 9060 and 8910 (pxGrid) only from the management VLAN. Drop and log everything else.
      • API hardening: Disable the ERS API and OpenAPI unless strictly required (Administration > System > Settings > API Settings). This shrinks attack surface but is not a substitute for patching.
      • IPS/NGFW: Update Cisco Secure Firewall/Snort rule packs to include coverage for CVE-2025-20281 and run them in blocking mode. Add a generic rule flagging shell metacharacters (;, |, `, $() inside JSON bodies of API requests to ISE IPs.
      • Egress control: Restrict ISE outbound traffic to required destinations only (AD, DNS, NTP, syslog, Cisco update servers). Deny the rest to break reverse shells and payload staging.
      • Availability planning: Because ISE gates network access, prepare a fallback (fail-open or critical-auth VLAN on switches) so isolation or patch reboots do not cause an uncontrolled outage.

    3. Runbook step 3

      Detection rules

      • Web/API logs: Look for unauthenticated POST/PUT requests to ISE API paths from outside the management network, especially bodies containing shell metacharacters or base64 blobs. SPL sketch: index=ise sourcetype=*ise* (method=POST OR method=PUT) NOT src_ip IN (mgmt_net) | stats count by src_ip, uri_path
      • Network telemetry (Zeek/Suricata): Flag new outbound sessions from ISE IPs to non-allow-listed destinations, i.e. conn.log where id.orig_h is an ISE node and id.resp_p or the destination is outside the baseline. Also flag DNS lookups from ISE to unfamiliar domains.
      • Host integrity: Review support bundles and CLI output for unexpected processes (sh, bash, curl, wget, nc, python spawned by Java/Tomcat), new files in /tmp or web directories, and new cron entries. Engage Cisco TAC where needed, since ISE does not run a full EDR agent.
      • ISE audit logs via syslog to SIEM: Watch for unexpected configuration changes, new admin or API accounts, altered network-device entries, or modified authorisation policies. Sigma shape: logsource: product: cisco_ise | detection: event_type: config_change AND user NOT IN known_admins
      • Follow-on activity: Anomalous LDAP/Kerberos use of the ISE AD join account indicates credential theft after root compromise. Watch Windows Event IDs 4624/4768/4769 for that account originating from hosts other than the ISE nodes.

    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
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    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
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    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 a specific API of Cisco ISE and Cisco ISE-PIC could allow an unauthenticated, remote attacker to execute arbitrary code on the underlying operating system as root. The attacker does not require any valid credentials to exploit this vulnerability. This vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by submitting a crafted API request. A successful exploit could allow the attacker to obtain root privileges on an affected device.

    Source: pwn.watch, NVD (NIST), certeu_advisory, cvelistv5, CISA KEV Catalog, CVE.org (MITRE), CSA/SingCERT

    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 Identity Services Engine Software
    • 3.3.0
    • 3.3 Patch 5
    • 3.3 Patch 2
    • 3.4.0
    • 3.3 Patch 4
    • 3.3 Patch 6
    • 3.3 Patch 3
    • 3.4 Patch 1
    • 3.3 Patch 1
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    ciscoidentity_services_engine
    • 3.3.0
    • 3.4.0
    • —
    • —
    ciscoidentity_services_engine_passive_identity_connector
    • 3.3.0
    • 3.4.0
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

      Class

      The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

      Entry at MITRE CWE-74

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Reference tagged as exploitzerodayinitiative.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • sec.cloudapps.cisco.comcisco-sa-ise-unauth-rce-ZAd2GnJ6Vendor advisory, pwn-watch
    • zerodayinitiative.comblog/2025/7/24/cve-2025-20281-cisco-ise-api-unauthenticated-rem…Exploit, Technical description, Exploit, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-20281government-resource, US government resource
    • pwn.watchpwn.watch: Cisco Identity Services Engine: 2 exploited vulnerabilities (CVE-2025-20281, CVE-2025-20337)pwn-watch
    • NVD (NIST)NVD: CVE-2025-20281pwn-watch
    • NVD (NIST)NVD: CVE-2025-20337pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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