CVE-2026-3446 (GCVE-0-2026-3446)

Vulnerability from cvelistv5 – Published: 2026-04-10 18:17 – Updated: 2026-04-10 18:26
VLAI?
Title
Base64 decoding stops at first padded quad by default
Summary
When calling base64.b64decode() or related functions the decoding process would stop after encountering the first padded quad regardless of whether there was more information to be processed. This can lead to data being accepted which may be processed differently by other implementations. Use "validate=True" to enable stricter processing of base64 data.
Severity ?
6 (Medium)
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Assigner
PSF
References
Impacted products
Vendor Product Version
Python Software Foundation CPython Affected: 0 , < 3.13.13 (python)
Affected: 3.14.0 , < 3.14.4 (python)
Affected: 3.15.0a1 , < 3.15.0a8 (python)
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Credits
Serhiy Storchaka
Show details on NVD website
To clipboard 

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          "repo": "https://github.com/python/cpython",
          "vendor": "Python Software Foundation",
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              "version": "0",
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            }
          ],
          "value": "When calling base64.b64decode() or related functions the decoding process would stop after encountering the first padded quad regardless of whether there was more information to be processed. This can lead to data being accepted which may be processed differently by other implementations. Use \"validate=True\" to enable stricter processing of base64 data."
        }
      ],
      "metrics": [
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
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            "vulnerabilityResponseEffort": "NOT_DEFINED"
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          "scenarios": [
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              "value": "GENERAL"
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      "providerMetadata": {
        "dateUpdated": "2026-04-10T18:26:41.904Z",
        "orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
        "shortName": "PSF"
      },
      "references": [
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          "tags": [
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          "url": "https://github.com/python/cpython/pull/145267"
        },
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          "url": "https://github.com/python/cpython/issues/145264"
        },
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          "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/"
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        }
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      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Base64 decoding stops at first padded quad by default",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
    "assignerShortName": "PSF",
    "cveId": "CVE-2026-3446",
    "datePublished": "2026-04-10T18:17:35.045Z",
    "dateReserved": "2026-03-02T16:15:14.567Z",
    "dateUpdated": "2026-04-10T18:26:41.904Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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  }
}


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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.