pysec - pysec-2020-142

pysec-2020-142

Vulnerability from pysec

Published

2020-10-19 13:15

Modified

2020-10-29 22:16

Details

A mis-handling of invalid unicode characters in the Java implementation of Tink versions prior to 1.5 allows an attacker to change the ID part of a ciphertext, which result in the creation of a second ciphertext that can decrypt to the same plaintext. This can be a problem with encrypting deterministic AEAD with a single key, and rely on a unique ciphertext-per-plaintext.

Impacted products

Name	purl
tink	pkg:pypi/tink

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "tink",
        "purl": "pkg:pypi/tink"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "93d839a5865b9d950dffdc9d0bc99b71280a8899"
            }
          ],
          "repo": "https://github.com/google/tink",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2020-8929",
    "GHSA-g5vf-v6wf-7w2r"
  ],
  "details": "A mis-handling of invalid unicode characters in the Java implementation of Tink versions prior to 1.5 allows an attacker to change the ID part of a ciphertext, which result in the creation of a second ciphertext that can decrypt to the same plaintext. This can be a problem with encrypting deterministic AEAD with a single key, and rely on a unique ciphertext-per-plaintext.",
  "id": "PYSEC-2020-142",
  "modified": "2020-10-29T22:16:00Z",
  "published": "2020-10-19T13:15:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r"
    },
    {
      "type": "FIX",
      "url": "https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899"
    }
  ]
}

ghsa-g5vf-v6wf-7w2r

Vulnerability from github

Published

2020-10-16 00:51

Modified

2025-06-05 16:44

Severity ?

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
6.9 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Summary

Ciphertext Malleability Issue in Tink Java

Details

Impact

Tink's Java version before 1.5 under some circumstances allowed attackers to change the key ID part of the ciphertext, resulting in the attacker creating a second ciphertext that will decrypt to the same plaintext. This can be a problem in particular in the case of encrypting with a deterministic AEAD with a single key, and relying on the fact that there is only a single valid ciphertext per plaintext.

No loss of confidentiality or loss of plaintext integrity occurs due to this problem, only ciphertext integrity is compromised.

Patches

The issue was fixed in this pull request.

Workarounds

The only workaround is to backport the fixing pull request.

Details

Tink uses the first five bytes of a ciphertext for a version byte and a four byte key ID. Since each key has a well defined prefix, this extends non-malleability properties (but technically not indistinguishability). However, in the Java version this prefix lookup used a hash map indexed by unicode strings instead of the byte array, which means that invalid Unicode characters would be replaced by U+FFFD by the Java API's default behavior. This means several different values for the five bytes would result in the same hash table key, which allows an attacker to exchange one invalid byte sequence for another, creating a mutated ciphertext that still decrypts (to the same plaintext).

Acknowledgements

We'd like to thank Peter Esbensen for finding this issue and raising it internally.

For more information

If you have any questions or comments about this advisory: * Open an issue in Tink

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "com.google.crypto.tink:tink"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2020-8929"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-176",
      "CWE-327"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2020-10-16T00:49:43Z",
    "nvd_published_at": "2020-10-19T13:15:13Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\nTink\u0027s Java version before 1.5 under some circumstances allowed attackers to change the key ID part of the ciphertext, resulting in the attacker creating a second ciphertext that will decrypt to the same plaintext. This can be a problem in particular in the case of encrypting with a deterministic AEAD with a single key, and relying on the fact that there is only a single valid ciphertext per plaintext.\n\nNo loss of confidentiality or loss of plaintext integrity occurs due to this problem, only ciphertext integrity is compromised.\n\n### Patches\nThe issue was fixed in this [pull request](https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899).\n\n### Workarounds\nThe only workaround is to backport the fixing [pull request](https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899).\n\n### Details\nTink uses the first five bytes of a ciphertext for a version byte and a four byte key ID. Since each key has a well defined prefix, this extends non-malleability properties (but technically not indistinguishability). However, in the Java version this prefix lookup used a hash map indexed by unicode strings instead of the byte array, which means that invalid Unicode characters would be [replaced by U+FFFD](https://en.wikipedia.org/wiki/UTF-8#Invalid_sequences_and_error_handling) by the [Java API\u0027s default behavior](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#String(byte[],%20java.nio.charset.Charset)). This means several different values for the five bytes would result in the same hash table key, which allows an attacker to exchange one invalid byte sequence for another, creating a mutated ciphertext that still decrypts (to the same plaintext).\n\n### Acknowledgements\nWe\u0027d like to thank Peter Esbensen for finding this issue and raising it internally.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [Tink](https://github.com/google/tink/issues)",
  "id": "GHSA-g5vf-v6wf-7w2r",
  "modified": "2025-06-05T16:44:52Z",
  "published": "2020-10-16T00:51:24Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-8929"
    },
    {
      "type": "WEB",
      "url": "https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/tink/PYSEC-2020-142.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Ciphertext Malleability Issue in Tink Java"
}

CVE-2020-8929 (GCVE-0-2020-8929)

Vulnerability from cvelistv5

Published

2020-10-19 12:15

Modified

2024-08-04 10:12

Severity ?

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CWE

CWE-176 - Improper Handling of Unicode Encoding

Summary

References

URL

Tags

	https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899	x_refsource_CONFIRM
	https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r	x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	Google LLC	Tink	Version: stable < 1.5

Show details on NVD website

JSON

To clipboard

{
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          "dateUpdated": "2024-08-04T10:12:11.052Z",
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            "url": "https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899"
          },
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            "url": "https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r"
          }
        ],
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      }
    ],
    "cna": {
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          "platforms": [
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          ],
          "product": "Tink",
          "vendor": "Google LLC",
          "versions": [
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      ],
      "credits": [
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      ],
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        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
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      "problemTypes": [
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      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "Ciphertext integrity weakness in Tink",
      "x_generator": {
        "engine": "Vulnogram 0.0.9"
      },
      "x_legacyV4Record": {
        "CVE_data_meta": {
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          "ID": "CVE-2020-8929",
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        },
        "affects": {
          "vendor": {
            "vendor_data": [
              {
                "product": {
                  "product_data": [
                    {
                      "product_name": "Tink",
                      "version": {
                        "version_data": [
                          {
                            "platform": "Java",
                            "version_affected": "\u003c",
                            "version_name": "stable",
                            "version_value": "1.5"
                          }
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                },
                "vendor_name": "Google LLC"
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}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
Confirmed: The vulnerability is confirmed from an analyst perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
Patched: This vulnerability was successfully patched by the user reporting the sighting.
Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
Not confirmed: The user expresses doubt about the veracity of the vulnerability.
Not patched: This vulnerability was not successfully patched by the user reporting the sighting.

Action not permitted

pysec-2020-142

Vulnerability from pysec

ghsa-g5vf-v6wf-7w2r

Vulnerability from github

Impact

Patches

Workarounds

Details

Acknowledgements

For more information

CVE-2020-8929 (GCVE-0-2020-8929)

Vulnerability from cvelistv5

Tags

Sightings

Nomenclature