CVE-2026-49263 (GCVE-0-2026-49263)
Vulnerability from cvelistv5 – Published: 2026-08-14 17:49 – Updated: 2026-08-14 17:49
VLAI
EPSS
VEX
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
CWE
- CWE-197 - Numeric Truncation Error
Assigner
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 | |
|---|---|---|---|
| capstone-engine | capstone |
Affected:
< 6.0.0-Alpha9
|
{
"containers": {
"cna": {
"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"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-49263",
"date": "2026-08-16",
"epss": "0.00128",
"percentile": "0.02891"
},
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}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
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.
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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