{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-5731", "assignerOrgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe", "state": "PUBLISHED", "assignerShortName": "mozilla", "dateReserved": "2026-04-07T12:43:11.413Z", "datePublished": "2026-04-07T12:43:11.895Z", "dateUpdated": "2026-04-07T18:25:20.392Z"}, "containers": {"cna": {"affected": [{"product": "Firefox", "vendor": "Mozilla", "versions": [{"lessThan": "149.0.2", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Firefox ESR", "vendor": "Mozilla", "versions": [{"lessThan": "115.34.1", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Firefox ESR", "vendor": "Mozilla", "versions": [{"lessThan": "140.9.1", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Thunderbird", "vendor": "Mozilla", "versions": [{"lessThan": "149.0.2", "status": "affected", "version": "unspecified", "versionType": "custom"}]}, {"product": "Thunderbird", "vendor": "Mozilla", "versions": [{"lessThan": "140.9.1", "status": "affected", "version": "unspecified", "versionType": "custom"}]}], "descriptions": [{"lang": "en", "value": "Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and Thunderbird < 140.9.1.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and Thunderbird < 140.9.1."}]}], "title": "Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2", "references": [{"url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=2021894%2C2022225%2C2022252%2C2022294%2C2023007%2C2023130%2C2023191%2C2023364%2C2023829%2C2024074%2C2024417%2C2024433%2C2024436%2C2024437%2C2024453%2C2024461%2C2024462%2C2024472%2C2024474%2C2024477%2C2025364%2C2025401%2C2025402%2C2025472%2C2026287%2C2026299%2C2026305%2C2026426", "name": "Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-25/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-26/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-27/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-28/"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-29/"}], "credits": [{"lang": "en", "value": "Brian Grinstead, Christian Holler, Tom Schuster and the Mozilla Fuzzing Team"}], "providerMetadata": {"orgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe", "shortName": "mozilla", "dateUpdated": "2026-04-07T18:25:20.392Z"}}, "adp": [{"problemTypes": [{"descriptions": [{"type": "CWE", "cweId": "CWE-119", "lang": "en", "description": "CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer"}]}], "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": "2026-04-07T14:12:57.462645Z", "id": "CVE-2026-5731", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"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": "2026-04-07T14:13:29.548Z"}}]}}

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