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Fencer Vulns
low 2.0

CVE-2026-49263 json

Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization

published 2026-08-14 2 mo ago modified 2026-09-18 51 d ago also EUVD-2026-58747

cvss
2.0
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits
0
none known

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.

Patch / fix

  • capstone hummingbird 1 5.0.8-0.5.hum1
  • capstone-java hummingbird 1 5.0.8-0.5.hum1
  • python3-capstone hummingbird 1 5.0.8-0.5.hum1

red hat advisories RHSA-2026:81540

  • rust Azure Linux 3.0 1.75.0-30
  • rust Azure Linux 3.0 1.90.0-10

azure linux advisories AZL-96734AZL-96743

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-49263 updated cvss 6.8

capstone: Capstone: Denial of Service and parser desynchronization via WebAssembly `br_table` instruction-size truncation

  • Red Hat Enterprise Linux 9 capstone, capstone-java, python3-capstone Red Hat Enterprise Linux 10 capstone Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images capstone 5.0.8-0.5.hum1, capstone-java 5.0.8-0.5.hum1, python3-capstone 5.0.8-0.5.hum1
    fixed: vendor fix RHSA-2026:81540

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 2.0 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
CNA 4.0 2.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • capstone-engine capstone

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.