pysec - pysec-2025-29

PYSEC-2025-29

Vulnerability from pysec - Published: 2025-02-21 22:15 - Updated: 2025-04-09 17:27

Details

vyper is a Pythonic Smart Contract Language for the EVM. Vyper sqrt() builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results. This issue is being addressed and a fix is expected in version 0.4.1. Users are advised to upgrade as soon as the patched release is available. There are no known workarounds for this vulnerability.

Impacted products

Name	purl
vyper	pkg:pypi/vyper

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "vyper",
        "purl": "pkg:pypi/vyper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0b1",
        "0.1.0b10",
        "0.1.0b11",
        "0.1.0b12",
        "0.1.0b13",
        "0.1.0b14",
        "0.1.0b15",
        "0.1.0b16",
        "0.1.0b17",
        "0.1.0b2",
        "0.1.0b3",
        "0.1.0b4",
        "0.1.0b5",
        "0.1.0b6",
        "0.1.0b7",
        "0.1.0b8",
        "0.1.0b9",
        "0.2.1",
        "0.2.10",
        "0.2.11",
        "0.2.12",
        "0.2.13",
        "0.2.14",
        "0.2.15",
        "0.2.16",
        "0.2.2",
        "0.2.3",
        "0.2.4",
        "0.2.5",
        "0.2.6",
        "0.2.7",
        "0.2.8",
        "0.2.9",
        "0.3.0",
        "0.3.1",
        "0.3.10",
        "0.3.10rc1",
        "0.3.10rc2",
        "0.3.10rc3",
        "0.3.10rc4",
        "0.3.10rc5",
        "0.3.2",
        "0.3.3",
        "0.3.4",
        "0.3.5",
        "0.3.6",
        "0.3.7",
        "0.3.8",
        "0.3.9",
        "0.4.0",
        "0.4.0b1",
        "0.4.0b2",
        "0.4.0b3",
        "0.4.0b4",
        "0.4.0b5",
        "0.4.0b6",
        "0.4.0rc1",
        "0.4.0rc2",
        "0.4.0rc3",
        "0.4.0rc4",
        "0.4.0rc5",
        "0.4.0rc6",
        "0.4.1b1",
        "0.4.1b2",
        "0.4.1b3",
        "0.4.1b4",
        "0.4.1rc1",
        "0.4.1rc2",
        "0.4.1rc3"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-26622",
    "GHSA-2p94-8669-xg86"
  ],
  "details": "vyper is a Pythonic Smart Contract Language for the EVM. Vyper `sqrt()` builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results. This issue is being addressed and a fix is expected in version 0.4.1. Users are advised to upgrade as soon as the patched release is available. There are no known workarounds for this vulnerability.",
  "id": "PYSEC-2025-29",
  "modified": "2025-04-09T17:27:28.005382+00:00",
  "published": "2025-02-21T22:15:13+00:00",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-2p94-8669-xg86"
    },
    {
      "type": "FIX",
      "url": "https://github.com/vyperlang/vyper/pull/4486"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/vyperlang/vyper/pull/4486"
    }
  ]
}

GHSA-2P94-8669-XG86

Vulnerability from github – Published: 2025-02-21 22:43 – Updated: 2025-04-09 20:11

Summary

Vyper's sqrt doesn't define rounding behavior

Details

Vyper's sqrt() builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results.

the fix is tracked in https://github.com/vyperlang/vyper/pull/4486

Vulnerability Details

Vyper injects the following code to handle calculation of decimal sqrt. x is the input provided by user.

assert x >= 0.0
z: decimal = 0.0

if x == 0.0:
    z = 0.0
else:
    z = x / 2.0 + 0.5
    y: decimal = x

    for i: uint256 in range(256):
        if z == y:
            break
        y = z
        z = (x / z + z) / 2.0

Notably, the terminal condition of the algorithm is either z_cur == z_prev, or the algorithm runs for 256 rounds.

However, for certain inputs, z might actually oscillate between N and N + epsilon, where N ** 2 <= x < (N + epsilon) ** 2. This means that the current behavior does not define whether it will round up or down to the nearest epsilon.

The example snippet here returns 0.9999999999, the rounded up result for sqrt(0.9999999998). This is due to the oscillation ending in N + epsilon instead of N.

@external
def test():
    d: decimal = 0.9999999998
    r: decimal = sqrt(d)    #this will be 0.9999999999

Note that sqrt() diverges from isqrt() here -- isqrt() consistently rounds down, so it is not subject to the same issue.

Impact Details

Since sqrt() can be used for determining boundary conditions, rounding down is preferred. However, since sqrt() is used very rarely in the wild, this advisory has been assigned an impact of low.

Severity ?

2.3 (Low)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.4.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "vyper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-26622"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-682"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-02-21T22:43:30Z",
    "nvd_published_at": "2025-02-21T22:15:13Z",
    "severity": "LOW"
  },
  "details": "Vyper\u0027s `sqrt()` builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results.\n\nthe fix is tracked in https://github.com/vyperlang/vyper/pull/4486\n\n### Vulnerability Details\n\nVyper injects the following code to handle calculation of decimal sqrt. x is the input provided by user.\n```python\nassert x \u003e= 0.0\nz: decimal = 0.0\n\nif x == 0.0:\n    z = 0.0\nelse:\n    z = x / 2.0 + 0.5\n    y: decimal = x\n\n    for i: uint256 in range(256):\n        if z == y:\n            break\n        y = z\n        z = (x / z + z) / 2.0\n```\nNotably, the terminal condition of the algorithm is either `z_cur == z_prev`, or the algorithm runs for 256 rounds.\n\nHowever, for certain inputs, `z` might actually oscillate between `N` and `N + epsilon`, where `N ** 2 \u003c= x \u003c (N + epsilon) ** 2`. This means that the current behavior does not define whether it will round up or down to the nearest epsilon.\n\nThe example snippet here returns 0.9999999999, the rounded up result for sqrt(0.9999999998). This is due to the oscillation ending in N + epsilon instead of N.\n```vyper\n@external\ndef test():\n    d: decimal = 0.9999999998\n    r: decimal = sqrt(d)    #this will be 0.9999999999\n```\n\nNote that `sqrt()` diverges from `isqrt()` here -- `isqrt()` consistently rounds down, so it is not subject to the same issue.\n\n### Impact Details\n\nSince `sqrt()` can be used for determining boundary conditions, rounding down is preferred. However, since `sqrt()` is used very rarely in the wild, this advisory has been assigned an impact of `low`.",
  "id": "GHSA-2p94-8669-xg86",
  "modified": "2025-04-09T20:11:26Z",
  "published": "2025-02-21T22:43:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-2p94-8669-xg86"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-26622"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/pull/4486"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2025-29.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/vyperlang/vyper"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Vyper\u0027s sqrt doesn\u0027t define rounding behavior"
}

CVE-2025-26622 (GCVE-0-2025-26622)

Vulnerability from cvelistv5 – Published: 2025-02-21 21:36 – Updated: 2025-02-22 15:34

Summary

vyper is a Pythonic Smart Contract Language for the EVM. Vyper `sqrt()` builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results. This issue is being addressed and a fix is expected in version 0.4.1. Users are advised to upgrade as soon as the patched release is available. There are no known workarounds for this vulnerability.

Severity ?

2.3 (Low)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

CWE

CWE-682 - Incorrect Calculation

Assigner

GitHub_M

References

URL

Tags

	https://github.com/vyperlang/vyper/security/advis…	x_refsource_CONFIRM
	https://github.com/vyperlang/vyper/pull/4486	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	vyperlang	vyper	Affected: < 0.4.1

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "NONE",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2025-26622",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-02-22T15:34:07.833820Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-02-22T15:34:42.831Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "vyper",
          "vendor": "vyperlang",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.4.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "vyper is a Pythonic Smart Contract Language for the EVM. Vyper `sqrt()` builtin uses the babylonian method to calculate square roots of decimals. Unfortunately, improper handling of the oscillating final states may lead to sqrt incorrectly returning rounded up results. This issue is being addressed and a fix is expected in version 0.4.1. Users are advised to upgrade as soon as the patched release is available. There are no known workarounds for this vulnerability."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 2.3,
            "baseSeverity": "LOW",
            "privilegesRequired": "LOW",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-682",
              "description": "CWE-682: Incorrect Calculation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-02-21T21:36:19.063Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/vyperlang/vyper/security/advisories/GHSA-2p94-8669-xg86",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-2p94-8669-xg86"
        },
        {
          "name": "https://github.com/vyperlang/vyper/pull/4486",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/vyperlang/vyper/pull/4486"
        }
      ],
      "source": {
        "advisory": "GHSA-2p94-8669-xg86",
        "discovery": "UNKNOWN"
      },
      "title": "sqrt doesn\u0027t define rounding behavior in Vyper"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2025-26622",
    "datePublished": "2025-02-21T21:36:19.063Z",
    "dateReserved": "2025-02-12T14:51:02.719Z",
    "dateUpdated": "2025-02-22T15:34:42.831Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}

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.

Action not permitted

PYSEC-2025-29

GHSA-2P94-8669-XG86

Vulnerability Details

Impact Details

CVE-2025-26622 (GCVE-0-2025-26622)

Tags

Sightings

Nomenclature