CVE-2026-119196 (GCVE-0-2026-119196)

Vulnerability from cvelistv5 – Published: 2026-10-29 19:44 – Updated: 2026-10-29 19:44
VLAI
Title
pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding
Summary
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. This issue is fixed in version 0.6.5.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7978 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
pyasn1 pyasn1 Affected: < 0.6.5
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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  "containers": {
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          "vendor": "pyasn1",
          "versions": [
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              "version": "\u003c 0.6.5"
            }
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          "lang": "en",
          "value": "pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. This issue is fixed in version 0.6.5."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-407",
              "description": "CWE-407: Inefficient Algorithmic Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-29T19:44:46.031Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5"
        },
        {
          "name": "https://github.com/pyasn1/pyasn1/pull/132",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/pyasn1/pyasn1/pull/132"
        },
        {
          "name": "https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c",
          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c"
        },
        {
          "name": "https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5"
        }
      ],
      "source": {
        "advisory": "GHSA-2qm8-x737-gmw5",
        "discovery": "UNKNOWN"
      },
      "title": "pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-119196",
    "datePublished": "2026-10-29T19:44:46.031Z",
    "dateReserved": "2026-10-29T16:04:48.728Z",
    "dateUpdated": "2026-10-29T19:44:46.031Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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        "affected": [
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                "vendor": "pyasn1",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 0.6.5"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. This issue is fixed in version 0.6.5."
          }
        ],
        "id": "CVE-2026-119196",
        "lastModified": "2026-10-29T20:17:30.770",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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              "impactScore": 3.6,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
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        },
        "published": "2026-10-29T20:17:30.770",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/pyasn1/pyasn1/pull/132"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Received",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-407"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    }
  }
}



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