FKIE_CVE-2026-40686

Vulnerability from fkie_nvd - Published: 2026-04-30 22:16 - Updated: 2026-05-01 17:44
Severity ?
3.7 (Low) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Summary
In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
References
cve@mitre.orghttps://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efcPatch
cve@mitre.orghttps://exim.org/static/doc/security/CVE-2026-40686.txtBroken Link
cve@mitre.orghttps://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessmentVendor Advisory
cve@mitre.orghttps://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory
Impacted products
Vendor Product Version
exim exim *
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "E48EAA99-95DA-4695-BBEA-16D09AA0A508",
              "versionEndExcluding": "4.99.2",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message."
    }
  ],
  "id": "CVE-2026-40686",
  "lastModified": "2026-05-01T17:44:15.677",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 3.7,
          "baseSeverity": "LOW",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 1.4,
        "source": "cve@mitre.org",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-04-30T22:16:25.787",
  "references": [
    {
      "source": "cve@mitre.org",
      "tags": [
        "Patch"
      ],
      "url": "https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc"
    },
    {
      "source": "cve@mitre.org",
      "tags": [
        "Broken Link"
      ],
      "url": "https://exim.org/static/doc/security/CVE-2026-40686.txt"
    },
    {
      "source": "cve@mitre.org",
      "tags": [
        "Vendor Advisory"
      ],
      "url": "https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment"
    },
    {
      "source": "cve@mitre.org",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "url": "https://www.openwall.com/lists/oss-security/2026/04/30/21"
    }
  ],
  "sourceIdentifier": "cve@mitre.org",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        }
      ],
      "source": "cve@mitre.org",
      "type": "Secondary"
    }
  ]
}


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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

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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.