High

quickjs — security advisory

Type: advisorySources: OSVAdvisory ID: UBUNTU-CVE-2025-62496

A vulnerability exists in the QuickJS engine's BigInt string parsing logic (js_bigint_from_string) when attempting to create a BigInt from a string with an excessively large number of digits. The function calculates the necessary number of bits (n_bits) required to store the BigInt using the formula: $$\text{n\_bits} = (\text{n\_digits} \times 27 + 7) / 8 \quad (\text{for radix 10})$$ * For large input strings (e.g., $79,536,432$ digits or more for base 10), the intermediate calculation $(\text{n\_digits} \times 27 + 7)$ exceeds the maximum value of a standard signed 32-bit integer, resulting in an Integer Overflow. * The resulting n_bits value becomes unexpectedly small or even negative due to this wrap-around. * This flawed n_bits is then used to compute n_limbs, the number of memory "limbs" needed for the BigInt object. Since n_bits is too small, the calculated n_limbs is also significantly underestimated. * The function proceeds to allocate a JSBigInt object using this underestimated n_limbs. * When the function later attempts to write the actual BigInt data into the allocated object, the small buffer size is quickly exceeded, leading to a Heap Out-of-Bounds Write as data is written past the end of the allocated r->tab array.

Products: quickjs
Affected versions: 2021.03.27-1, 2021.03.27-1ubuntu0.1~esm1, 2024.01.13-5, 2025.04.26-1, 2025.04.26-1build1
Fixed versions: Not specified
CVEs: CVE-2025-62496
Confirmed fixed CVEs: Not specified
Updated in this feed: 31 Oct 2026, 01:44 UTC · Revision 1

Source evidence

UBUNTU-CVE-2025-62496

core-osv · Original source

Published 16 Oct 2025, 16:15 UTC

osv:UBUNTU-CVE-2025-62496

quickjs

Fixed versions: Not specified

quickjs

Fixed versions: Not specified

quickjs

Fixed versions: Not specified

quickjs

Fixed versions: Not specified

Complete source record

{
  "id": "257eaf90f80375a99573f0dc0d5029b7871f47591175a977316a89b6a01af207",
  "url": "https://osv.dev/vulnerability/UBUNTU-CVE-2025-62496",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "UBUNTU-CVE-2025-62496",
    "summary": "A vulnerability exists in the QuickJS engine's BigInt string parsing logic (js_bigint_from_string) when attempting to create a BigInt from a string with an excessively large number of digits. The function calculates the necessary number of bits (n_bits) required to store the BigInt using the formula: $$\\text{n\\_bits} = (\\text{n\\_digits} \\times 27 + 7) / 8 \\quad (\\text{for radix 10})$$ * For large input strings (e.g., $79,536,432$ digits or more for base 10), the intermediate calculation $(\\text{n\\_digits} \\times 27 + 7)$ exceeds the maximum value of a standard signed 32-bit integer, resulting in an Integer Overflow. * The resulting n_bits value becomes unexpectedly small or even negative due to this wrap-around. * This flawed n_bits is then used to compute n_limbs, the number of memory \"limbs\" needed for the BigInt object. Since n_bits is too small, the calculated n_limbs is also significantly underestimated. * The function proceeds to allocate a JSBigInt object using this underestimated n_limbs. * When the function later attempts to write the actual BigInt data into the allocated object, the small buffer size is quickly exceeded, leading to a Heap Out-of-Bounds Write as data is written past the end of the allocated r->tab array.",
    "evidence": "osv:UBUNTU-CVE-2025-62496",
    "products": [
      {
        "name": {
          "value": "quickjs",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "2021.03.27-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "2021.03.27-1ubuntu0.1~esm1",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "quickjs",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "2024.01.13-5",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "2025.04.26-1",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "quickjs",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "2025.04.26-1build1",
            "evidence": "/affected/2/versions"
          }
        ]
      },
      {
        "name": {
          "value": "quickjs",
          "evidence": "/affected/3/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "2025.04.26-1",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "2025.04.26-1build1",
            "evidence": "/affected/3/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "UBUNTU-CVE-2025-62496",
      "aliases": [
        "UBUNTU-CVE-2025-62496"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:A/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L"
        },
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        },
        {
          "type": "Ubuntu",
          "score": "medium"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "quickjs",
            "purl": "pkg:deb/ubuntu/quickjs?arch=source&distro=esm-apps%2Fnoble",
            "ecosystem": "Ubuntu:Pro:24.04:LTS"
          },
          "versions": [
            "2021.03.27-1",
            "2021.03.27-1ubuntu0.1~esm1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libquickjs",
                "binary_version": "2021.03.27-1ubuntu0.1~esm1"
              },
              {
                "binary_name": "quickjs",
                "binary_version": "2021.03.27-1ubuntu0.1~esm1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "quickjs",
            "purl": "pkg:deb/ubuntu/quickjs?arch=source&distro=questing",
            "ecosystem": "Ubuntu:25.10"
          },
          "versions": [
            "2024.01.13-5",
            "2025.04.26-1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libquickjs",
                "binary_version": "2025.04.26-1"
              },
              {
                "binary_name": "quickjs",
                "binary_version": "2025.04.26-1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "quickjs",
            "purl": "pkg:deb/ubuntu/quickjs?arch=source&distro=stonking",
            "ecosystem": "Ubuntu:26.10"
          },
          "versions": [
            "2025.04.26-1build1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libquickjs",
                "binary_version": "2025.04.26-1build1"
              },
              {
                "binary_name": "quickjs",
                "binary_version": "2025.04.26-1build1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "quickjs",
            "purl": "pkg:deb/ubuntu/quickjs?arch=source&distro=resolute",
            "ecosystem": "Ubuntu:26.04:LTS"
          },
          "versions": [
            "2025.04.26-1",
            "2025.04.26-1build1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libquickjs",
                "binary_version": "2025.04.26-1build1"
              },
              {
                "binary_name": "quickjs",
                "binary_version": "2025.04.26-1build1"
              }
            ]
          }
        }
      ],
      "modified": "2026-10-17T12:57:22.271133574Z",
      "provider": "osv",
      "upstream": [
        "CVE-2025-62496"
      ],
      "references": [
        "https://ubuntu.com/security/CVE-2025-62496",
        "https://www.cve.org/CVERecord?id=CVE-2025-62496",
        "https://issuetracker.google.com/434193016",
        "https://bellard.org/quickjs/Changelog"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2025-62496",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/1/score"
  },
  "source_id": "core-osv",
  "document_id": 357355,
  "published_at": "2025-10-16T16:15:00+00:00"
}