{ "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-2026-34872", "tracking": { "current_release_date": "2026-04-02T15:05:21.321279Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34872", "initial_release_date": "2026-04-01T19:38:44.220938Z", "revision_history": [ { "date": "2026-04-01T19:38:44.220938Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| References created (2)." }, { "date": "2026-04-01T19:38:46.122300Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-01T20:38:46.344273Z", "number": "3", "summary": "CVSS created.| CWES updated (1).| Unknown change." }, { "date": "2026-04-01T20:38:48.597687Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-01T23:27:45.752790Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)." }, { "date": "2026-04-01T23:27:49.040512Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-04-02T12:27:59.566971Z", "number": "7", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1).| Vendor_assessment created." }, { "date": "2026-04-02T12:28:03.571287Z", "number": "8", "summary": "NCSC Score updated." }, { "date": "2026-04-02T12:45:59.912102Z", "number": "9", "summary": "Source created.| CVE status created. (valid)| Description created for source.| Products connected (2)." }, { "date": "2026-04-02T12:46:07.799926Z", "number": "10", "summary": "NCSC Score updated." }, { "date": "2026-04-02T14:58:50.444806Z", "number": "11", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-02T14:58:53.341154Z", "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-2026-34872", "cwe": { "id": "CWE-347", "name": "Improper Verification of Cryptographic Signature" }, "notes": [ { "category": "description", "text": "An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34872.json" }, { "category": "description", "text": "An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34872" }, { "category": "description", "text": "An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).\nA flaw was found in Mbed TLS and TF-PSA-Crypto. This vulnerability, stemming from improper input validation in the finite-field Diffie-Hellman (FFDH) key exchange, allows a remote attacker to force the shared secret into a small, predictable set of values. This lack of contributory behavior can compromise the security of protocols that rely on the uniqueness and unpredictability of shared secrets, potentially enabling further attacks.\nAn Important flaw exists in Mbed TLS and TF-PSA-Crypto due to improper input validation in the finite-field Diffie-Hellman (FFDH) key exchange. This allows a remote attacker to influence the shared secret to a small set of values, impacting protocols that rely on strong contributory behavior. Notably, the TLS protocol is not affected by this specific issue.", "title": "redhat - https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-34872.json" }, { "category": "description", "text": "An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).", "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-34872" }, { "category": "other", "text": "0.00021", "title": "EPSS" }, { "category": "other", "text": "3.6", "title": "NCSC Score" }, { "category": "other", "text": "Is related to CWE-1287 (Improper Validation of Specified Type of Input)", "title": "NCSC Score top increasing factors" }, { "category": "other", "text": "There is cwe data available from source Nvd, Is related to (a version of) an uncommon product, The value of the most recent EPSS score", "title": "NCSC Score top decreasing factors" }, { "category": "details", "text": "Severity: 3\n", "title": "Vendor assessment" } ], "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-2026-34872.json" }, { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34872" }, { "category": "external", "summary": "Source - redhat", "url": "https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-34872.json" }, { "category": "external", "summary": "Source - debian", "url": "https://security-tracker.debian.org/tracker/CVE-2026-34872" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; nvd; redhat", "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/" }, { "category": "external", "summary": "Reference - cveprojectv5; nvd; redhat", "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/" }, { "category": "external", "summary": "Reference - redhat", "url": "https://www.cve.org/CVERecord?id=CVE-2026-34872" }, { "category": "external", "summary": "Reference - redhat", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34872" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 9.1, "baseSeverity": "CRITICAL" }, "products": [ "CSAFPID-2559460", "CSAFPID-2559461" ] } ], "title": "CVE-2026-34872" } ] }