CVE-2025-12781 (GCVE-0-2025-12781)

Vulnerability from cvelistv5 – Published: 2026-01-21 19:34 – Updated: 2026-01-22 20:12
VLAI?
Title
base64.b64decode() always accepts "+/" characters, despite setting altchars
Summary
When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues. This behavior can only be insecure if your application uses an alternate base64 alphabet (without "+/"). If your application does not use the "altchars" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet. The attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python. Users are recommended to mitigate by verifying user-controlled inputs match the base64 alphabet they are expecting or verify that their application would not be affected if the b64decode() functions accepted "+" or "/" outside of altchars.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CWE
  • CWE-704 - Incorrect Type Conversion or Cast
Assigner
PSF
References
Impacted products
Vendor Product Version
Python Software Foundation CPython Affected: 0 , < 3.13.10 (python)
Affected: 3.14.0 , < 3.14.1 (python)
Affected: 3.15.0a1 , < 3.15.0a2 (python)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-12781",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-01-22T14:53:47.177224Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-704",
                "description": "CWE-704 Incorrect Type Conversion or Cast",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-01-22T14:53:50.663Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "base64"
          ],
          "product": "CPython",
          "repo": "https://github.com/python/cpython",
          "vendor": "Python Software Foundation",
          "versions": [
            {
              "lessThan": "3.13.10",
              "status": "affected",
              "version": "0",
              "versionType": "python"
            },
            {
              "lessThan": "3.14.1",
              "status": "affected",
              "version": "3.14.0",
              "versionType": "python"
            },
            {
              "lessThan": "3.15.0a2",
              "status": "affected",
              "version": "3.15.0a1",
              "versionType": "python"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cdiv\u003eWhen passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the \"base64\" module the characters \"+/\" will always be accepted, regardless of the value of \"altchars\" parameter, typically used to establish an \"alternative base64 alphabet\" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.\u003c/div\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003eThis behavior can only be insecure if your application uses an alternate base64 alphabet (without \"+/\"). If your application does not use the \"altchars\" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.\u003c/div\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003eThe attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python.\u0026nbsp;Users are recommended to mitigate by verifying user-controlled inputs match the base64 \nalphabet they are expecting or verify that their application would not be \naffected if the b64decode() functions accepted \"+\" or \"/\" outside of altchars.\u003c/div\u003e"
            }
          ],
          "value": "When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the \"base64\" module the characters \"+/\" will always be accepted, regardless of the value of \"altchars\" parameter, typically used to establish an \"alternative base64 alphabet\" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.\n\n\n\n\nThis behavior can only be insecure if your application uses an alternate base64 alphabet (without \"+/\"). If your application does not use the \"altchars\" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.\n\n\n\n\nThe attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python.\u00a0Users are recommended to mitigate by verifying user-controlled inputs match the base64 \nalphabet they are expecting or verify that their application would not be \naffected if the b64decode() functions accepted \"+\" or \"/\" outside of altchars."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "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:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-22T20:12:56.421Z",
        "orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
        "shortName": "PSF"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/pull/141128"
        },
        {
          "tags": [
            "issue-tracking"
          ],
          "url": "https://github.com/python/cpython/issues/125346"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/KRI7GC6S27YV5NJ4FPDALS2WI5ENAFJ6/"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/13360efd385d1a7d0659beba03787ea3d063ef9b"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/1be80bec7960f5ccd059e75f3dfbd45fca302947"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/9060b4abbe475591b6230b23c2afefeff26fcca5"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/e95e783dff443b68e8179fdb57737025bf02ba76"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/python/cpython/commit/fd17ee026fa9b67f6288cbafe374a3e479fe03a5"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "base64.b64decode() always accepts \"+/\" characters, despite setting altchars",
      "x_generator": {
        "engine": "Vulnogram 0.5.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
    "assignerShortName": "PSF",
    "cveId": "CVE-2025-12781",
    "datePublished": "2026-01-21T19:34:47.979Z",
    "dateReserved": "2025-11-05T22:04:54.230Z",
    "dateUpdated": "2026-01-22T20:12:56.421Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-12781\",\"sourceIdentifier\":\"cna@python.org\",\"published\":\"2026-01-21T20:16:04.423\",\"lastModified\":\"2026-02-02T17:25:23.933\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the \\\"base64\\\" module the characters \\\"+/\\\" will always be accepted, regardless of the value of \\\"altchars\\\" parameter, typically used to establish an \\\"alternative base64 alphabet\\\" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.\\n\\n\\n\\n\\nThis behavior can only be insecure if your application uses an alternate base64 alphabet (without \\\"+/\\\"). If your application does not use the \\\"altchars\\\" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.\\n\\n\\n\\n\\nThe attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python.\u00a0Users are recommended to mitigate by verifying user-controlled inputs match the base64 \\nalphabet they are expecting or verify that their application would not be \\naffected if the b64decode() functions accepted \\\"+\\\" or \\\"/\\\" outside of altchars.\"}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"cna@python.org\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":6.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"LOW\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"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:N/I:L/A:N\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-704\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:python:python:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"3.13.10\",\"matchCriteriaId\":\"B02C195C-8271-4207-9FE9-E46C7A4978AE\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:python:python:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"3.14.0\",\"versionEndExcluding\":\"3.14.1\",\"matchCriteriaId\":\"6E66BA7A-987F-4E24-8B69-4F46D6FCD19E\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:python:python:3.15.0:alpha1:*:*:*:*:*:*\",\"matchCriteriaId\":\"A3327507-0B1D-4F28-A983-D07A2C8A7696\"}]}]}],\"references\":[{\"url\":\"https://github.com/python/cpython/commit/13360efd385d1a7d0659beba03787ea3d063ef9b\",\"source\":\"cna@python.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/python/cpython/commit/1be80bec7960f5ccd059e75f3dfbd45fca302947\",\"source\":\"cna@python.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/python/cpython/commit/9060b4abbe475591b6230b23c2afefeff26fcca5\",\"source\":\"cna@python.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/python/cpython/commit/e95e783dff443b68e8179fdb57737025bf02ba76\",\"source\":\"cna@python.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/python/cpython/commit/fd17ee026fa9b67f6288cbafe374a3e479fe03a5\",\"source\":\"cna@python.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/python/cpython/issues/125346\",\"source\":\"cna@python.org\",\"tags\":[\"Exploit\",\"Issue Tracking\"]},{\"url\":\"https://github.com/python/cpython/pull/141128\",\"source\":\"cna@python.org\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://mail.python.org/archives/list/security-announce@python.org/thread/KRI7GC6S27YV5NJ4FPDALS2WI5ENAFJ6/\",\"source\":\"cna@python.org\",\"tags\":[\"Mailing List\",\"Vendor Advisory\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2025-12781\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-01-22T14:53:47.177224Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-704\", \"description\": \"CWE-704 Incorrect Type Conversion or Cast\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-01-22T14:53:14.185Z\"}}], \"cna\": {\"title\": \"base64.b64decode() always accepts \\\"+/\\\" characters, despite setting altchars\", \"source\": {\"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 6.3, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N\", \"exploitMaturity\": \"NOT_DEFINED\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"repo\": \"https://github.com/python/cpython\", \"vendor\": \"Python Software Foundation\", \"modules\": [\"base64\"], \"product\": \"CPython\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"3.13.10\", \"versionType\": \"python\"}, {\"status\": \"affected\", \"version\": \"3.14.0\", \"lessThan\": \"3.14.1\", \"versionType\": \"python\"}, {\"status\": \"affected\", \"version\": \"3.15.0a1\", \"lessThan\": \"3.15.0a2\", \"versionType\": \"python\"}], \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://github.com/python/cpython/pull/141128\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/issues/125346\", \"tags\": [\"issue-tracking\"]}, {\"url\": \"https://mail.python.org/archives/list/security-announce@python.org/thread/KRI7GC6S27YV5NJ4FPDALS2WI5ENAFJ6/\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://github.com/python/cpython/commit/13360efd385d1a7d0659beba03787ea3d063ef9b\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/1be80bec7960f5ccd059e75f3dfbd45fca302947\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/9060b4abbe475591b6230b23c2afefeff26fcca5\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/e95e783dff443b68e8179fdb57737025bf02ba76\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/python/cpython/commit/fd17ee026fa9b67f6288cbafe374a3e479fe03a5\", \"tags\": [\"patch\"]}], \"x_generator\": {\"engine\": \"Vulnogram 0.5.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the \\\"base64\\\" module the characters \\\"+/\\\" will always be accepted, regardless of the value of \\\"altchars\\\" parameter, typically used to establish an \\\"alternative base64 alphabet\\\" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.\\n\\n\\n\\n\\nThis behavior can only be insecure if your application uses an alternate base64 alphabet (without \\\"+/\\\"). If your application does not use the \\\"altchars\\\" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.\\n\\n\\n\\n\\nThe attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python.\\u00a0Users are recommended to mitigate by verifying user-controlled inputs match the base64 \\nalphabet they are expecting or verify that their application would not be \\naffected if the b64decode() functions accepted \\\"+\\\" or \\\"/\\\" outside of altchars.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cdiv\u003eWhen passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the \\\"base64\\\" module the characters \\\"+/\\\" will always be accepted, regardless of the value of \\\"altchars\\\" parameter, typically used to establish an \\\"alternative base64 alphabet\\\" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.\u003c/div\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003eThis behavior can only be insecure if your application uses an alternate base64 alphabet (without \\\"+/\\\"). If your application does not use the \\\"altchars\\\" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.\u003c/div\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003eThe attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python.\u0026nbsp;Users are recommended to mitigate by verifying user-controlled inputs match the base64 \\nalphabet they are expecting or verify that their application would not be \\naffected if the b64decode() functions accepted \\\"+\\\" or \\\"/\\\" outside of altchars.\u003c/div\u003e\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"28c92f92-d60d-412d-b760-e73465c3df22\", \"shortName\": \"PSF\", \"dateUpdated\": \"2026-01-22T20:12:56.421Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-12781\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-22T20:12:56.421Z\", \"dateReserved\": \"2025-11-05T22:04:54.230Z\", \"assignerOrgId\": \"28c92f92-d60d-412d-b760-e73465c3df22\", \"datePublished\": \"2026-01-21T19:34:47.979Z\", \"assignerShortName\": \"PSF\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

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.