CVE-2026-5734 (GCVE-0-2026-5734)

Vulnerability from cvelistv5 – Published: 2026-04-07 12:43 – Updated: 2026-05-26 18:14
VLAI
Title
Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2
Summary
Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-120 - Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Assigner
References
Impacted products
Vendor Product Version
Mozilla Firefox Unaffected: 140.9.1 , ≤ 140.* (rpm)
Unaffected: 149.0.2 , ≤ * (rpm)
Create a notification for this product.
Mozilla Thunderbird Unaffected: 140.9.1 , ≤ 140.* (rpm)
Unaffected: 149.0.2 , ≤ * (rpm)
Create a notification for this product.
Credits
Brian Grinstead, Christian Holler, Tom Schuster and the Mozilla Fuzzing Team
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "HIGH",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 8.1,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-5734",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-08T03:55:30.963374Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-120",
                "description": "CWE-120 Buffer Copy without Checking Size of Input (\u0027Classic Buffer Overflow\u0027)",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-26T18:14:09.229Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "Firefox",
          "vendor": "Mozilla",
          "versions": [
            {
              "lessThanOrEqual": "140.*",
              "status": "unaffected",
              "version": "140.9.1",
              "versionType": "rpm"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "149.0.2",
              "versionType": "rpm"
            }
          ]
        },
        {
          "product": "Thunderbird",
          "vendor": "Mozilla",
          "versions": [
            {
              "lessThanOrEqual": "140.*",
              "status": "unaffected",
              "version": "140.9.1",
              "versionType": "rpm"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "149.0.2",
              "versionType": "rpm"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Brian Grinstead, Christian Holler, Tom Schuster and the Mozilla Fuzzing Team"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1."
            }
          ],
          "value": "Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-13T13:51:34.677Z",
        "orgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
        "shortName": "mozilla"
      },
      "references": [
        {
          "name": "Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2",
          "url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=2022369%2C2023026%2C2023545%2C2023555%2C2023958%2C2025422%2C2025468%2C2025492%2C2025505"
        },
        {
          "url": "https://www.mozilla.org/security/advisories/mfsa2026-25/"
        },
        {
          "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/"
        }
      ],
      "title": "Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
    "assignerShortName": "mozilla",
    "cveId": "CVE-2026-5734",
    "datePublished": "2026-04-07T12:43:14.833Z",
    "dateReserved": "2026-04-07T12:43:14.328Z",
    "dateUpdated": "2026-05-26T18:14:09.229Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-5734",
      "date": "2026-06-04",
      "epss": "0.00065",
      "percentile": "0.20301"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-5734\",\"sourceIdentifier\":\"security@mozilla.org\",\"published\":\"2026-04-07T13:16:47.667\",\"lastModified\":\"2026-04-13T15:17:46.820\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"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\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.2,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]},{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-120\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*\",\"versionEndExcluding\":\"140.9.1\",\"matchCriteriaId\":\"68770777-CF92-4F1C-A7FB-874344D23D39\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*\",\"versionEndExcluding\":\"149.0.2\",\"matchCriteriaId\":\"CF910B3C-C241-48B5-9066-260750E8E7ED\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*\",\"versionEndExcluding\":\"140.9.1\",\"matchCriteriaId\":\"2D9A64DA-C9F4-4EFC-A3C8-84C442DD4B6A\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*\",\"versionEndExcluding\":\"149.0.2\",\"matchCriteriaId\":\"5FB6BDEF-D9FC-4C5C-9098-03DCA98223D3\"}]}]}],\"references\":[{\"url\":\"https://bugzilla.mozilla.org/buglist.cgi?bug_id=2022369%2C2023026%2C2023545%2C2023555%2C2023958%2C2025422%2C2025468%2C2025492%2C2025505\",\"source\":\"security@mozilla.org\",\"tags\":[\"Broken Link\",\"Issue Tracking\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2026-25/\",\"source\":\"security@mozilla.org\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2026-27/\",\"source\":\"security@mozilla.org\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2026-28/\",\"source\":\"security@mozilla.org\"},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2026-29/\",\"source\":\"security@mozilla.org\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 8.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-5734\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-04-08T03:55:30.963374Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-120\", \"description\": \"CWE-120 Buffer Copy without Checking Size of Input (\u0027Classic Buffer Overflow\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-04-13T13:20:24.604Z\"}}], \"cna\": {\"title\": \"Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2\", \"credits\": [{\"lang\": \"en\", \"value\": \"Brian Grinstead, Christian Holler, Tom Schuster and the Mozilla Fuzzing Team\"}], \"affected\": [{\"vendor\": \"Mozilla\", \"product\": \"Firefox\", \"versions\": [{\"status\": \"unaffected\", \"version\": \"140.9.1\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"140.*\"}, {\"status\": \"unaffected\", \"version\": \"149.0.2\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"*\"}]}, {\"vendor\": \"Mozilla\", \"product\": \"Thunderbird\", \"versions\": [{\"status\": \"unaffected\", \"version\": \"140.9.1\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"140.*\"}, {\"status\": \"unaffected\", \"version\": \"149.0.2\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"*\"}]}], \"references\": [{\"url\": \"https://bugzilla.mozilla.org/buglist.cgi?bug_id=2022369%2C2023026%2C2023545%2C2023555%2C2023958%2C2025422%2C2025468%2C2025492%2C2025505\", \"name\": \"Memory safety bugs fixed in 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/mfsa2026-27/\"}, {\"url\": \"https://www.mozilla.org/security/advisories/mfsa2026-28/\"}, {\"url\": \"https://www.mozilla.org/security/advisories/mfsa2026-29/\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"f16b083a-5664-49f3-a51e-8d479e5ed7fe\", \"shortName\": \"mozilla\", \"dateUpdated\": \"2026-04-13T13:51:34.677Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-5734\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-26T18:14:09.229Z\", \"dateReserved\": \"2026-04-07T12:43:14.328Z\", \"assignerOrgId\": \"f16b083a-5664-49f3-a51e-8d479e5ed7fe\", \"datePublished\": \"2026-04-07T12:43:14.833Z\", \"assignerShortName\": \"mozilla\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.