CVE-2026-34872

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{"affected": [{"affectedData": [{"product": "n/a", "vendor": "n/a", "versions": [{"status": "affected", "version": "n/a"}]}], "source": "cve@mitre.org"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*", "matchCriteriaId": "C8FBFC2E-329D-4274-A952-2D43378B83BD", "versionEndExcluding": "3.6.6", "vulnerable": true}, {"criteria": "cpe:2.3:a:arm:tf-psa-crypto:1.0.0:-:*:*:*:*:*:*", "matchCriteriaId": "874FFF30-23C9-453A-8E82-037AD3F12345", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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)."}], "id": "CVE-2026-34872", "lastModified": "2026-06-17T10:39:46.057", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.2, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-34872", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-01T19:51:10.004400Z", "version": "2.0.3"}}]}, "published": "2026-04-01T20:16:27.493", "references": [{"source": "cve@mitre.org", "tags": ["Vendor Advisory"], "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/"}, {"source": "cve@mitre.org", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/"}], "sourceIdentifier": "cve@mitre.org", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-347"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "mbedtls: Mbed TLS and TF-PSA-Crypto: Shared secret manipulation via improper FFDH input validation", "id": "2453966", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2453966"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "status": "draft"}, "cwe": "CWE-1287", "details": ["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).", "A 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."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-34872", "public_date": "2026-04-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-34872\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-34872\nhttps://mbed-tls.readthedocs.io/en/latest/security-advisories/\nhttps://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/"], "statement": "An 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.", "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.5.0,3.6.0)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.6.0,3.6.5]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "original": {"product": "n/a", "source": "cna", "vendor": "n/a"}, "product": "mbedtls", "vendor": "mbed-tls"}], "analysis": {"en": {"generated_at": "2026-04-03T23:54:11.213079+00:00", "value": {"mitigation_remediation": ["Upgrade ARM Mbed TLS to a patched release that includes the FFDHE input validation fix and update TF\u2011PSA\u2011Crypto to a fixed version if available. ", "If the upgrade is not feasible, verify whether the deployed system uses any cryptographic protocols that depend on contributory behavior in Diffie\u2011Hellman. Disable those protocols or switch to an alternative key\u2011exchange mechanism that does not rely on contributory behavior. ", "Monitor network traffic for abnormal Diffie\u2011Hellman key exchanges and apply general hardening practices, such as disabling legacy cryptographic primitives and ensuring TLS configurations avoid weak cipher suites."], "summary": {"action": "Immediate Patch", "impact": "Manipulation of Derived Keys"}, "threat_synthesis": {"affected_systems": "Products affected are the ARM Mbed TLS library in the 3.5.x to 3.6.5 series and the TF\u2011PSA\u2011Crypto 1.0.0 implementation. These libraries are embedded in many IoT devices, secure elements, and other systems that perform finite\u2011field Diffie\u2011Hellman key exchanges. The flaw applies wherever these libraries are used to exchange keys in protocols that rely on contributory behavior; TLS itself is not impacted because it does not depend on contribution for key establishment.", "description_and_impact": "The vulnerability arises from inadequate validation of finite\u2011field Diffie\u2011Hellman peer key inputs in Mbed TLS versions 3.5.x through 3.6.5 and TF\u2011PSA\u2011Crypto 1.0.0, allowing a malicious peer to force the negotiated shared secret into a limited, predictable set of values. This lack of contributory behavior permits an attacker to influence the symmetric key used for subsequent encryption, potentially compromising confidentiality of the protected communication. The issue is rooted in improper input validation (CWE-1287) and mishandling of cryptographic protocols (CWE-347).", "risk_and_exploitability": "The CVSS score of 9.1 indicates a severe risk if exploited, while an EPSS score below 1\u202f% suggests exploitation is unlikely but possible. The vulnerability is not listed in CISA\u2019s Known Exploited Vulnerabilities catalog. Exploitation does not require local privileges; an attacker can act as a peer or perform a man\u2011in\u2011the\u2011middle attack to supply malicious parameters. Successful exploitation would alter the derived key, allowing compromised confidentiality of any data encrypted with that key.\n"}}}}, "created": "2026-04-02T07:51:13.644179+00:00", "updated": "2026-04-07T08:07:41.600056+00:00", "vendors": ["mbed-tls", "mbed-tls$PRODUCT$mbedtls"]}