Vulnerability-Lookup

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

Vulnerability from cvelistv5 – Published: 2026-08-14 17:49 – Updated: 2026-08-17 19:52

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.

Severity

2 (Low)


                        
                          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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-17 19:51 UTC

CWE

CWE-197 - Numeric Truncation Error

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7752 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/capstone-engine/capstone/secur…	x_refsource_CONFIRM
https://github.com/capstone-engine/capstone/blob/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
capstone-engine	capstone	Affected: < 6.0.0-Alpha9	guessed

Show details on NVD website

JSON

To clipboard

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}

FKIE_CVE-2026-49263

Vulnerability from fkie_nvd - Published: 2026-08-14 18:17 - Updated: 2026-09-18 20:05

Severity

2.0 (Low) - 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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/capstone-engine/capstone/blob/251c5bb4bc9bb92973e738ae3c5f4ef86f103356/ChangeLog#L102
	security-advisories@github.com	https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "capstone",
          "vendor": "capstone-engine",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.0.0-Alpha9"
            }
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    }
  ],
  "id": "CVE-2026-49263",
  "lastModified": "2026-09-18T20:05:53.723",
  "metrics": {
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          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
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          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
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}

RHSA-2026:81540

Vulnerability from csaf_redhat - Published: 2026-10-12 21:09 - Updated: 2026-10-16 11:28

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Severity

Moderate

Scope

2 vulnerabilities in this advisory, including CVE-2026-49263.

CVE-2026-49263

A flaw was found in Capstone, a disassembly framework, affecting its WebAssembly (WASM) backend. A remote attacker could exploit this by providing a specially crafted `br_table` instruction. This could lead to a denial of service, where the disassembler gets stuck in a loop, or cause parser desynchronization, leading to incorrect disassembly of subsequent instructions. This issue impacts the availability and integrity of the disassembler.

6.8 (Medium)


                
                  CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Fixed: 16 products

https://access.redhat.com/errata/RHSA-2026:81540

Open the full advisory

UBUNTU-CVE-2026-49263 (CVE-2026-49263)

Vulnerability from osv_ubuntu – Published: 2026-08-14 18:17 – Updated: 2026-08-19 11:05 – Source website

Details

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.

Severity

2.0 (Low)


                    
                      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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-49263	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-49263	REPORT
	https://github.com/capstone-engine/capstone/secur…	REPORT
	https://github.com/capstone-engine/capstone/blob/…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libcapstone3",
            "binary_version": "3.0.4-0.2"
          },
          {
            "binary_name": "python-capstone",
            "binary_version": "3.0.4-0.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@3.0.4-0.2?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.0.4-0.1",
        "3.0.4-0.2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libcapstone3",
            "binary_version": "3.0.4-5"
          },
          {
            "binary_name": "python-capstone",
            "binary_version": "3.0.4-5"
          },
          {
            "binary_name": "python3-capstone",
            "binary_version": "3.0.4-5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@3.0.4-5?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.0.4-3",
        "3.0.4-5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "capstone-tool",
            "binary_version": "4.0.1+really+3.0.5-1build1"
          },
          {
            "binary_name": "libcapstone3",
            "binary_version": "4.0.1+really+3.0.5-1build1"
          },
          {
            "binary_name": "python-capstone",
            "binary_version": "4.0.1+really+3.0.5-1build1"
          },
          {
            "binary_name": "python3-capstone",
            "binary_version": "4.0.1+really+3.0.5-1build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@4.0.1+really+3.0.5-1build1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.1+really+3.0.5-1",
        "4.0.1+really+3.0.5-1build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "capstone-tool",
            "binary_version": "4.0.2-5"
          },
          {
            "binary_name": "libcapstone4",
            "binary_version": "4.0.2-5"
          },
          {
            "binary_name": "python3-capstone",
            "binary_version": "4.0.2-5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@4.0.2-5?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.2-3",
        "4.0.2-3build1",
        "4.0.2-5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "capstone-tool",
            "binary_version": "4.0.2-5.1build1"
          },
          {
            "binary_name": "libcapstone4",
            "binary_version": "4.0.2-5.1build1"
          },
          {
            "binary_name": "python3-capstone",
            "binary_version": "4.0.2-5.1build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@4.0.2-5.1build1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.2-5",
        "4.0.2-5ubuntu1",
        "4.0.2-5.1",
        "4.0.2-5.1build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "capstone-tool",
            "binary_version": "5.0.7-2"
          },
          {
            "binary_name": "libcapstone5",
            "binary_version": "5.0.7-2"
          },
          {
            "binary_name": "python3-capstone",
            "binary_version": "5.0.7-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "capstone",
        "purl": "pkg:deb/ubuntu/capstone@5.0.7-2?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.0.6-1",
        "5.0.6-1build1",
        "5.0.7-2"
      ]
    }
  ],
  "aliases": [],
  "details": "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.",
  "id": "UBUNTU-CVE-2026-49263",
  "modified": "2026-08-19T11:05:28Z",
  "published": "2026-08-14T18:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-49263"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-49263"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/capstone-engine/capstone/blob/251c5bb4bc9bb92973e738ae3c5f4ef86f103356/ChangeLog#L102"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-49263"
  ]
}

Sightings

Author	Source	Type	Date	Other

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.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

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

FKIE_CVE-2026-49263

RHSA-2026:81540

UBUNTU-CVE-2026-49263 (CVE-2026-49263)

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