{"api_version":"1","generated_at":"2026-07-23T14:56:42+00:00","cve":"CVE-2026-4721","urls":{"html":"https://cve.report/CVE-2026-4721","api":"https://cve.report/api/cve/CVE-2026-4721.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-4721","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-4721"},"summary":{"title":"Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149","description":"Memory safety bugs present in Firefox ESR 115.33, 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. 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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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}],"value":"Memory safety bugs present in Firefox ESR 115.33, 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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}],"providerMetadata":{"dateUpdated":"2026-04-13T13:51:21.639Z","orgId":"f16b083a-5664-49f3-a51e-8d479e5ed7fe","shortName":"mozilla"},"references":[{"name":"Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149","url":"https://bugzilla.mozilla.org/buglist.cgi?bug_id=2013762%2C2015291%2C2016591%2C2016661%2C2016664%2C2017303%2C2017894%2C2018090%2C2018196%2C2018379%2C2019112%2C2022090%2C2022243%2C2022351%2C2022478%2C2022676"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-20/"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-21/"},{"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/"}],"title":"Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149"}},"cveMetadata":{"assignerOrgId":"f16b083a-5664-49f3-a51e-8d479e5ed7fe","assignerShortName":"mozilla","cveId":"CVE-2026-4721","datePublished":"2026-03-24T12:30:44.312Z","dateReserved":"2026-03-23T23:22:42.445Z","dateUpdated":"2026-07-15T00:49:07.514Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-03-24 13:16:07","lastModifiedDate":"2026-07-15 02:22:51","problem_types":["CWE-120","CWE-825","CWE-120 CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')","CWE-825 Expired Pointer Dereference"],"metrics":{"cvssMetricV31":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9},{"source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.6,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-03-25T03:56:11.360250Z","id":"CVE-2026-4721","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*","versionEndExcluding":"115.34.0","matchCriteriaId":"063BE653-69B0-4543-9A90-BC7A62C943B5"},{"vulnerable":true,"criteria":"cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*","versionEndExcluding":"149.0","matchCriteriaId":"02F2B82F-E997-4D5F-BBB0-237E4962555B"},{"vulnerable":true,"criteria":"cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*","versionStartIncluding":"128.0","versionEndExcluding":"140.9.0","matchCriteriaId":"525DEC0C-BB47-46C6-9AEB-98F27D4685FE"},{"vulnerable":true,"criteria":"cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*","versionEndExcluding":"140.9.0","matchCriteriaId":"4C0558B1-4113-45A8-8E37-A0793A67AD6D"},{"vulnerable":true,"criteria":"cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*","versionEndExcluding":"149.0","matchCriteriaId":"40FE4697-89F1-46F6-8E28-41883647583B"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"4721","Ordinal":"1","Title":"Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.","CVE":"CVE-2026-4721","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"4721","Ordinal":"1","NoteData":"Memory safety bugs present in Firefox ESR 115.33, 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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.","Type":"Description","Title":"Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140."}]}}}