{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-4720", "assignerOrgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe", "state": "PUBLISHED", "assignerShortName": "mozilla", "dateReserved": "2026-03-23T23:22:41.974Z", "datePublished": "2026-03-24T12:30:43.271Z", "dateUpdated": "2026-03-25T13:10:13.381Z"}, "containers": {"cna": {"affected": [{"product": "Firefox", "vendor": "Mozilla", "versions": [{"lessThan": "149", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Firefox ESR", "vendor": "Mozilla", "versions": [{"lessThan": "140.9", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Thunderbird", "vendor": "Mozilla", "versions": [{"lessThan": "149", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Thunderbird", "vendor": "Mozilla", "versions": [{"lessThan": "140.9", "status": "affected", "version": "unspecified", "versionType": "custom"}]}], "descriptions": [{"lang": "en", "value": "Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9."}]}], "title": "Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149", "references": [{"url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=2004652%2C2019372%2C2021922%2C2022567%2C2022733", "name": "Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-22/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/"}], "credits": [{"lang": "en", "value": "Christian Holler, Gabriele Svelto, Tom Schuster and the Mozilla Fuzzing Team"}], "providerMetadata": {"orgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe", "shortName": "mozilla", "dateUpdated": "2026-03-24T20:27:54.765Z"}}, "adp": [{"problemTypes": [{"descriptions": [{"type": "CWE", "cweId": "CWE-120", "lang": "en", "description": "CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')"}]}], "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.8, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"timestamp": "2026-03-25T03:56:10.337285Z", "id": "CVE-2026-4720", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-03-25T13:10:13.381Z"}}]}}

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{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "matchCriteriaId": "DA62D95E-CB01-4586-83DB-5094116FC939", "versionEndExcluding": "140.9.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B", "versionEndExcluding": "149.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*", "matchCriteriaId": "4C0558B1-4113-45A8-8E37-A0793A67AD6D", "versionEndExcluding": "140.9.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*", "matchCriteriaId": "40FE4697-89F1-46F6-8E28-41883647583B", "versionEndExcluding": "149.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9."}, {"lang": "es", "value": "Errores de seguridad de memoria presentes en Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 y Thunderbird 148. Algunos de estos errores mostraron evidencia de corrupci\u00f3n de memoria y presumimos que con suficiente esfuerzo algunos de estos podr\u00edan haber sido explotados para ejecutar c\u00f3digo arbitrario. Esta vulnerabilidad afecta a Firefox &lt; 149, Firefox ESR &lt; 140.9, Thunderbird &lt; 149 y Thunderbird &lt; 140.9."}], "id": "CVE-2026-4720", "lastModified": "2026-03-25T20:56:19.130", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "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:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}, "published": "2026-03-24T13:16:07.893", "references": [{"source": "security@mozilla.org", "tags": ["Broken Link"], "url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=2004652%2C2019372%2C2021922%2C2022567%2C2022733"}, {"source": "security@mozilla.org", "tags": ["Vendor Advisory"], "url": "https://www.mozilla.org/security/advisories/mfsa2026-20/"}, {"source": "security@mozilla.org", "tags": ["Vendor Advisory"], "url": "https://www.mozilla.org/security/advisories/mfsa2026-22/"}, {"source": "security@mozilla.org", "tags": ["Vendor Advisory"], "url": "https://www.mozilla.org/security/advisories/mfsa2026-23/"}, {"source": "security@mozilla.org", "tags": ["Vendor Advisory"], "url": "https://www.mozilla.org/security/advisories/mfsa2026-24/"}], "sourceIdentifier": "security@mozilla.org", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-120"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149", "id": "2450751", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2450751"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-120", "details": ["A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:\nMemory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code."], "name": "CVE-2026-4720", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "rhel10/firefox-flatpak", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "rhel10/thunderbird-flatpak", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "firefox", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "thunderbird", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-03-24T12:30:43Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-4720\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-4720\nhttps://www.mozilla.org/security/advisories/mfsa2026-22/#CVE-2026-4720\nhttps://www.mozilla.org/security/advisories/mfsa2026-24/#CVE-2026-4720"], "statement": "Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.", "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,149)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Firefox", "source": "cna", "vendor": "Mozilla"}, "product": "firefox", "vendor": "mozilla"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,140.9)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Firefox ESR", "source": "cna", "vendor": "Mozilla"}, "product": "firefox_esr", "vendor": "mozilla"}], "analysis": {"en": {"generated_at": "2026-03-25T14:39:02.567642+00:00", "value": {"mitigation_remediation": ["Upgrade to Firefox 149 or newer, or to Firefox ESR 140.9 or newer.", "Upgrade to Thunderbird 149 or newer, or to Thunderbird ESR 140.9 or newer.", "Verify that the update has been successfully applied on all affected systems.", "If upgrading immediately is not possible, refrain from browsing untrusted web content or opening untrusted emails until the patch is applied."], "summary": {"action": "Immediate Patch", "impact": "Remote code execution via memory corruption"}, "threat_synthesis": {"affected_systems": "Products affected are Mozilla Firefox and Thunderbird, including the extended support releases (ESR). Versions prior to Firefox 149, ESR 140.9, Thunderbird 149 and ESR 140.9 are impacted.", "description_and_impact": "The vulnerability is a memory safety bug that resulted in memory corruption and could allow an attacker to execute arbitrary code. The weakness corresponds to CWE-120, indicating a buffer copy without checking input length.", "risk_and_exploitability": "The CVSS score of 9.8 classifies this flaw as critical; however, the EPSS score is below 1%, suggesting a low probability of exploitation so far. It is not listed in the CISA KEV catalog. The likely attack vector is an attacker delivering crafted content\u2014such as a malicious web page or email\u2014to a user running one of the vulnerable browsers, exploiting the memory corruption to achieve code execution. The attack requires that the user process the malicious input, so it is a user\u2011interaction vulnerability."}}}}, "created": "2026-03-25T11:47:44.277449+00:00", "updated": "2026-03-25T20:50:22.772830+00:00", "vendors": ["mozilla", "mozilla$PRODUCT$firefox", "mozilla$PRODUCT$firefox_esr"]}