CVE-2026-49263 (GCVE-0-2026-49263)

Vulnerability from cvelistv5 – Published: 2026-08-14 17:49 – Updated: 2026-08-14 17:49
VLAI
Title
Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization
Summary
Capstone is a disassembly framework. Prior to version 6.0.0-Alpha9, Capstone's WebAssembly backend accepts attacker-controlled raw WASM instruction bytes through the public `cs_disasm()` and `cs_disasm_iter()` APIs. For a large but well-formed `br_table` instruction, the WASM decoder accumulates the immediate length in a wider local variable but returns it through a `uint16_t` instruction-size path. When the encoded instruction length is exactly 65,536 bytes, the size wraps to zero and `cs_disasm()` can repeatedly decode the same instruction without advancing. For larger lengths, `cs_disasm_iter()` advances into the middle of the `br_table` payload and decodes target bytes as subsequent instructions. This is an availability and parser-integrity issue. Version 6.0.0-Alpha9 patches the issue.
CWE
  • CWE-197 - Numeric Truncation Error
Assigner
References
Impacted products
Vendor Product Version
capstone-engine capstone Affected: < 6.0.0-Alpha9
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Show details on NVD website

{
  "containers": {
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      "affected": [
        {
          "product": "capstone",
          "vendor": "capstone-engine",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.0.0-Alpha9"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Capstone is a disassembly framework. Prior to version 6.0.0-Alpha9, Capstone\u0027s WebAssembly backend accepts attacker-controlled raw WASM instruction bytes through the public `cs_disasm()` and `cs_disasm_iter()` APIs. For a large but well-formed `br_table` instruction, the WASM decoder accumulates the immediate length in a wider local variable but returns it through a `uint16_t` instruction-size path. When the encoded instruction length is exactly 65,536 bytes, the size wraps to zero and `cs_disasm()` can repeatedly decode the same instruction without advancing. For larger lengths, `cs_disasm_iter()` advances into the middle of the `br_table` payload and decodes target bytes as subsequent instructions. This is an availability and parser-integrity issue. Version 6.0.0-Alpha9 patches the issue."
        }
      ],
      "metrics": [
        {
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            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "LOCAL",
            "baseScore": 2,
            "baseSeverity": "LOW",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
            "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-197",
              "description": "CWE-197: Numeric Truncation Error",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-14T17:49:36.804Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr"
        },
        {
          "name": "https://github.com/capstone-engine/capstone/blob/251c5bb4bc9bb92973e738ae3c5f4ef86f103356/ChangeLog#L102",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/capstone-engine/capstone/blob/251c5bb4bc9bb92973e738ae3c5f4ef86f103356/ChangeLog#L102"
        }
      ],
      "source": {
        "advisory": "GHSA-5m9f-vqcm-g5pr",
        "discovery": "UNKNOWN"
      },
      "title": "Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-49263",
    "datePublished": "2026-08-14T17:49:36.804Z",
    "dateReserved": "2026-05-28T14:33:01.180Z",
    "dateUpdated": "2026-08-14T17:49:36.804Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-08-16",
      "epss": "0.00128",
      "percentile": "0.02891"
    },
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  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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