CVE-2026-25834

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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:trustedfirmware:mbed_tls:*:*:*:*:*:*:*:*", "matchCriteriaId": "EC5F3123-A3E0-4CDC-AE3F-A859253C357A", "versionEndExcluding": "3.6.6", "versionStartIncluding": "3.3.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:trustedfirmware:mbed_tls:4.0.0:*:*:*:*:*:*:*", "matchCriteriaId": "26ECBD35-D500-4CF2-A7F5-0C91A5F39274", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade."}, {"lang": "es", "value": "Mbed TLS v3.3.0 hasta 3.6.5 y 4.0.0 permite la degradaci\u00f3n de algoritmo."}], "id": "CVE-2026-25834", "lastModified": "2026-11-11T19:10:00.360", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 2.5, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-25834", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-01T18:53:56.370902Z", "version": "2.0.3"}}]}, "published": "2026-04-01T18:16:28.127", "references": [{"source": "cve@mitre.org", "tags": ["Vendor Advisory"], "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/"}, {"source": "cve@mitre.org", "tags": ["Vendor Advisory"], "url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-sigalg-injection/"}], "sourceIdentifier": "cve@mitre.org", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-295"}, {"lang": "en", "value": "CWE-327"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "mbedtls: Mbed TLS: Algorithm downgrade vulnerability", "id": "2453967", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2453967"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L", "status": "draft"}, "cwe": "CWE-358", "details": ["Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.", "A flaw was found in Mbed TLS. A remote attacker could exploit this vulnerability by performing an algorithm downgrade attack. This could lead to a reduction in the security strength of cryptographic operations, potentially allowing for information disclosure or denial of service."], "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-2026-25834", "public_date": "2026-04-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-25834\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-25834\nhttps://mbed-tls.readthedocs.io/en/latest/security-advisories/\nhttps://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-sigalg-injection/"], "statement": "Moderate: This flaw in Mbed TLS allows a remote attacker to perform an algorithm downgrade attack, which can reduce the security strength of cryptographic operations. This could potentially lead to information disclosure or denial of service. This vulnerability affects community projects such as Fedora and EPEL.", "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.3.0,3.6.5]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "4.0.0"}}], "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": "2026-04-06T16:37:08.487669+00:00", "value": {"mitigation_remediation": ["Upgrade Mbed TLS to the latest version that addresses the algorithm downgrade issue.", "Verify the upgraded library by testing cryptographic operations to ensure strong algorithms are enforced.", "If an upgrade is not immediately feasible, monitor vendor advisories for additional patches or workarounds and apply interim security controls such as disabling weaker algorithm options in configuration."], "summary": {"action": "Patch", "impact": "Algorithm Downgrade"}, "threat_synthesis": {"affected_systems": "ARM\u2019s Mbed TLS library, widely deployed in embedded and IoT devices, is affected. The vulnerability spans releases 3.3.0 up to 3.6.5 and the 4.0.0 major line. Systems relying on these versions\u2014including embedded firmware, network appliances, and connected sensors\u2014must assess whether the vulnerable library is in use.", "description_and_impact": "The flaw exists in Mbed TLS versions 3.3.0 through 3.6.5 and 4.0.0, enabling an attacker to force the library to use a weaker cryptographic algorithm. The downgrade bypasses expected security parameters, potentially allowing cryptographic keys to be derived in an unsuitable form or breaking data integrity. The associated Common Weakness identifiers highlight improper certificate validation, use of risky algorithms, and selection of weak cryptographic primitives.", "risk_and_exploitability": "With a CVSS base score of 6.5 the issue is considered moderate severity; however, exploitation likelihood is low according to the EPSS metric (<1%) and the vulnerability is not currently listed in the CISA KEV catalog. Successful exploitation would require the attacker to supply crafted algorithm identifiers, which suggests a remote configuration or protocol\u2011level vector, though precise conditions are not detailed in the advisory. Vulnerable deployments lacking updated cryptographic material thus face risk of weakened encryption or authentication."}}}}, "created": "2026-04-02T07:51:27.598835+00:00", "updated": "2026-04-07T08:07:46.635068+00:00", "vendors": ["mbed-tls", "mbed-tls$PRODUCT$mbedtls"]}