{
    "document": {
        "category": "csaf_base",
        "csaf_version": "2.0",
        "distribution": {
            "tlp": {
                "label": "WHITE"
            }
        },
        "lang": "en",
        "notes": [
            {
                "category": "legal_disclaimer",
                "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
            }
        ],
        "publisher": {
            "category": "coordinator",
            "contact_details": "cert@ncsc.nl",
            "name": "National Cyber Security Centre",
            "namespace": "https://www.ncsc.nl/"
        },
        "title": "CVE-2026-34876",
        "tracking": {
            "current_release_date": "2026-04-03T15:35:59.446249Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-34876",
            "initial_release_date": "2026-04-02T15:39:10.822338Z",
            "revision_history": [
                {
                    "date": "2026-04-02T15:39:10.822338Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| References created (2)."
                },
                {
                    "date": "2026-04-02T15:39:13.474929Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                },
                {
                    "date": "2026-04-02T16:26:10.020816Z",
                    "number": "3",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| References created (2)."
                },
                {
                    "date": "2026-04-02T16:38:55.761075Z",
                    "number": "4",
                    "summary": "CVSS created.| CWES updated (1).| Unknown change."
                },
                {
                    "date": "2026-04-02T16:38:57.108612Z",
                    "number": "5",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-04-02T17:28:13.565379Z",
                    "number": "6",
                    "summary": "CVSS created.| CWES updated (1)."
                },
                {
                    "date": "2026-04-02T17:28:18.124749Z",
                    "number": "7",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-04-03T00:43:44.377645Z",
                    "number": "8",
                    "summary": "Source created.| CVE status created. (valid)| Products connected (2)."
                },
                {
                    "date": "2026-04-03T00:43:51.682938Z",
                    "number": "9",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-04-03T06:43:50.569374Z",
                    "number": "10",
                    "summary": "Description created for source."
                },
                {
                    "date": "2026-04-03T15:30:43.610222Z",
                    "number": "11",
                    "summary": "Source connected.| CVE status created. (valid)| EPSS created."
                },
                {
                    "date": "2026-04-03T15:30:50.010667Z",
                    "number": "12",
                    "summary": "NCSC Score updated."
                }
            ],
            "status": "interim",
            "version": "12"
        }
    },
    "product_tree": {
        "branches": [
            {
                "branches": [
                    {
                        "branches": [
                            {
                                "branches": [
                                    {
                                        "category": "product_version_range",
                                        "name": "vers:deb/unknown",
                                        "product": {
                                            "name": "vers:deb/unknown",
                                            "product_id": "CSAFPID-2559460"
                                        }
                                    }
                                ],
                                "category": "product_name",
                                "name": "mbedtls"
                            }
                        ],
                        "category": "product_family",
                        "name": "bookworm"
                    },
                    {
                        "branches": [
                            {
                                "branches": [
                                    {
                                        "category": "product_version_range",
                                        "name": "vers:deb/unknown",
                                        "product": {
                                            "name": "vers:deb/unknown",
                                            "product_id": "CSAFPID-2559461"
                                        }
                                    }
                                ],
                                "category": "product_name",
                                "name": "mbedtls"
                            }
                        ],
                        "category": "product_family",
                        "name": "bullseye"
                    }
                ],
                "category": "vendor",
                "name": "Debian"
            }
        ]
    },
    "vulnerabilities": [
        {
            "cve": "CVE-2026-34876",
            "cwe": {
                "id": "CWE-125",
                "name": "Out-of-bounds Read"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.",
                    "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34876.json"
                },
                {
                    "category": "description",
                    "text": "An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.",
                    "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34876"
                },
                {
                    "category": "description",
                    "text": "An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.",
                    "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-34876"
                },
                {
                    "category": "other",
                    "text": "0.00017",
                    "title": "EPSS"
                },
                {
                    "category": "other",
                    "text": "3.5",
                    "title": "NCSC Score"
                },
                {
                    "category": "other",
                    "text": "The value of the most recent EPSS score, Is related to (a version of) an uncommon product, There is cwe data available from source Nvd",
                    "title": "NCSC Score top decreasing factors"
                }
            ],
            "product_status": {
                "known_affected": [
                    "CSAFPID-2559460",
                    "CSAFPID-2559461"
                ]
            },
            "references": [
                {
                    "category": "external",
                    "summary": "Source - cveprojectv5",
                    "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34876.json"
                },
                {
                    "category": "external",
                    "summary": "Source - nvd",
                    "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34876"
                },
                {
                    "category": "external",
                    "summary": "Source - debian",
                    "url": "https://security-tracker.debian.org/tracker/CVE-2026-34876"
                },
                {
                    "category": "external",
                    "summary": "Source - first",
                    "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; nvd",
                    "url": "https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; nvd",
                    "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/"
                }
            ],
            "scores": [
                {
                    "cvss_v3": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
                        "baseScore": 7.5,
                        "baseSeverity": "HIGH"
                    },
                    "products": [
                        "CSAFPID-2559460",
                        "CSAFPID-2559461"
                    ]
                }
            ],
            "title": "CVE-2026-34876"
        }
    ]
}