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CVE-2021-40540

Status: ModifiedCritical (9.8)—
Severity9.8Critical · CVSS 3.1
Exploitation probability2.63 %higher than 85% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

ulfius_uri_logger in Ulfius HTTP Framework before 2.7.4 omits con_info initialization and a con_info->request NULL check for certain malformed HTTP requests.

CVSS

Base score
9.8
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
2.63 %
Percentile among all scored CVEs
85
Score date
10/24/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Ulfius Project — Ulfius

CWEs

References

Show 6 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-40540",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 7.5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "HIGH",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
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    "cvssMetricV31": [
      {
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        "cvssData": {
          "scope": "UNCHANGED",
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          "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"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
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      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
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  ],
  "published": "2021-09-07T02:15:07.130",
  "references": [
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      "url": "http://packetstormsecurity.com/files/164152/Ulfius-Web-Framework-Remote-Memory-Corruption.html",
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      "url": "https://github.com/babelouest/ulfius/compare/v2.7.3...v2.7.4",
      "tags": [
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        "Third Party Advisory"
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      "source": "cve@mitre.org"
    },
    {
      "url": "http://packetstormsecurity.com/files/164152/Ulfius-Web-Framework-Remote-Memory-Corruption.html",
      "tags": [
        "Exploit",
        "Third Party Advisory",
        "VDB Entry"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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    {
      "url": "https://github.com/babelouest/ulfius/commit/c83f564c184a27145e07c274b305cabe943bbfaa",
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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      "url": "https://github.com/babelouest/ulfius/compare/v2.7.3...v2.7.4",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "ulfius_uri_logger in Ulfius HTTP Framework before 2.7.4 omits con_info initialization and a con_info->request NULL check for certain malformed HTTP requests."
    },
    {
      "lang": "es",
      "value": "la función ulfius_uri_logger en Ulfius HTTP Framework antes de la versión 2.7.4 omite la inicialización de con_info y la comprobación de con_info-)request NULL para determinadas peticiones HTTP malformadas"
    }
  ],
  "lastModified": "2026-06-17T04:07:06.640",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:ulfius_project:ulfius:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "5C8CFDCE-F4D2-487C-9672-597FC6DD79E5",
              "versionEndExcluding": "2.7.4"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}