{
  "document": {
    "acknowledgments": [
      {
        "names": [
          "Shahriyar Jalayeri"
        ],
        "organization": "ByteRay Ltd",
        "summary": "reported this vulnerability to CISA"
      }
    ],
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Disclosure is not limited",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.cisa.gov/news-events/news/traffic-light-protocol-tlp-definitions-and-usage"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "legal_disclaimer",
        "text": "This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy).",
        "title": "Legal Notice and Terms of Use"
      },
      {
        "category": "summary",
        "text": "Successful exploitation of this vulnerability could allow an attacker to gain full code execution on the device. ",
        "title": "Advisory Summary"
      },
      {
        "category": "other",
        "text": "Chemical, Communications, Critical Manufacturing, Energy, Financial Services, Healthcare and Public Health, Transportation Systems, Water and Wastewater Systems",
        "title": "Critical infrastructure sectors"
      },
      {
        "category": "other",
        "text": "Worldwide",
        "title": "Countries/areas deployed"
      },
      {
        "category": "other",
        "text": "Sweden",
        "title": "Company headquarters location"
      },
      {
        "category": "general",
        "text": "CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Locate control system networks and remote devices behind firewalls and isolating them from business networks.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA also recommends users take the following measures to protect themselves from social engineering attacks:",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Do not click web links or open attachments in unsolicited email messages.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.",
        "title": "Recommended Practices"
      }
    ],
    "publisher": {
      "category": "coordinator",
      "contact_details": "central@cisa.dhs.gov",
      "name": "CISA",
      "namespace": "https://www.cisa.gov/"
    },
    "references": [
      {
        "category": "self",
        "summary": "ICS Advisory ICSA-26-265-01 JSON",
        "url": "https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2026/icsa-26-265-01.json"
      },
      {
        "category": "self",
        "summary": "ICSA Advisory ICSA-26-265-01 - Web Version",
        "url": "https://www.cisa.gov/news-events/ics-advisories/icsa-26-265-01"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/uscert/ics/alerts/ICS-ALERT-10-301-01"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/resources-tools/resources/ics-recommended-practices"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/sites/default/files/publications/Cybersecurity_Best_Practices_for_Industrial_Control_Systems.pdf"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/topics/industrial-control-systems"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/uscert/sites/default/files/publications/emailscams0905.pdf"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/uscert/ncas/tips/ST04-014"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/news-events/news/targeted-cyber-intrusion-detection-and-mitigation-strategies-update-b"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/secure-our-world/teach-employees-avoid-phishing"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/news-events/news/avoiding-social-engineering-and-phishing-attacks"
      }
    ],
    "title": "lwIP TCP/IP Stack MQTT Client Application",
    "tracking": {
      "current_release_date": "2026-09-22T06:00:00.000000Z",
      "generator": {
        "date": "2026-09-21T14:54:59.583702Z",
        "engine": {
          "name": "CISA CSAF Generator",
          "version": "1.0.0"
        }
      },
      "id": "ICSA-26-265-01",
      "initial_release_date": "2026-09-22T06:00:00.000000Z",
      "revision_history": [
        {
          "date": "2026-09-22T06:00:00.000000Z",
          "legacy_version": "Initial",
          "number": "1",
          "summary": "Initial Publication"
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": ">=2.0.1|<=2.2.1",
                "product": {
                  "name": "lwIP MQTT Client Application: >=2.0.1|<=2.2.1",
                  "product_id": "CSAFPID-0001"
                }
              }
            ],
            "category": "product_name",
            "name": "MQTT Client Application"
          }
        ],
        "category": "vendor",
        "name": "lwIP"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-87121",
      "cwe": {
        "id": "CWE-787",
        "name": "Out-of-bounds Write"
      },
      "notes": [
        {
          "category": "summary",
          "text": "The affected product is vulnerable to an out-of-bounds write, which may allow an attacker to gain full code execution on the device.",
          "title": "Vulnerability Summary"
        },
        {
          "category": "details",
          "text": "SSVCv2/E:N/A:Y/2026-09-21T06:00:00.000000Z",
          "title": "SSVC"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-0001"
        ]
      },
      "references": [
        {
          "category": "external",
          "summary": "cwe.mitre.org",
          "url": "https://cwe.mitre.org/data/definitions/787.html"
        },
        {
          "category": "external",
          "summary": "www.cve.org",
          "url": "https://www.cve.org/CVERecord?id=CVE-2026-87121"
        },
        {
          "category": "external",
          "summary": "www.first.org",
          "url": "https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        },
        {
          "category": "external",
          "summary": "www.first.org",
          "url": "https://www.first.org/cvss/calculator/4.0#CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "remediations": [
        {
          "category": "mitigation",
          "details": "Users of lwIP are encouraged to update their version of lwIP using the repository found at https://savannah.nongnu.org/projects/lwip. The commit identifier that contains the fix is f89407ea711879c04d91c92b35d67be78bbaf0f1.",
          "product_ids": [
            "CSAFPID-0001"
          ],
          "url": "https://savannah.nongnu.org/projects/lwip"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "products": [
            "CSAFPID-0001"
          ]
        }
      ]
    }
  ]
}