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Security Digest · Vulnerability record

CVE-2026-115893: Wasmtime: Cranelift backend on aarch64 can jump to incorrect target on large Wasm `br_table` instruction

Wasmtime is a runtime for WebAssembly. Prior to 36.0.19, 48.0.7, and 49.0.4, the Cranelift compiler backend on aarch64 can compile a Wasm brtable instruction with more than approximately 256,000 targets so that it has an incorrect conditional branch target.

CVSS 9.9 Critical EPSS 0.4% · p37 Check exposure

Updated By erroneo.us Security Desk14 references

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

  • No confirmed exploitation. It is not in CISA’s KEV catalog. That can change quickly after a public write-up; re-check if you are affected.
  • EPSS 0.4%, percentile 37: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 37% of all scored CVEs (low). EPSS is a probability, not a verdict.
  • Needs an account (low (any account)). Exposure depends on who can log in.
  • Editorial verdict: Check exposure. Wasmtime: Two CVSS 9.9 Cranelift Sandbox Escapes — If you run WebAssembly you did not write, especially on ARM64, treat this as an urgent sandbox-escape fix and rebuild. If you only run your own trusted modules, update on a normal schedule.

What it is

Wasmtime is a runtime for WebAssembly. Prior to 36.0.19, 48.0.7, and 49.0.4, the Cranelift compiler backend on aarch64 can compile a Wasm brtable instruction with more than approximately 256,000 targets so that it has an incorrect conditional branch target. The branch can then jump to arbitrary other code at a user-controlled offset, allowing a user-controlled Wasm module to escape the sandbox on aarch64 engines using the default Cranelift backend. This issue is fixed in versions 36.0.19, 48.0.7, and 49.0.4.

Weakness type: CWE-691.

Product: bytecodealliance wasmtime · Assigned by: GitHub_M · Published: 2026-10-23

Affected and fixed versions

VendorProductAffected versions (per CVE record)
bytecodealliancewasmtime< 36.0.19, >= 37.0.0, < 48.0.7, >= 49.0.0, < 49.0.4

Severity scores

Scored byCVSSScoreVector
GitHub_M3.19.9 CriticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
  • Attack vector: network (remotely reachable)
  • Attack complexity: low
  • Privileges required: low (any account)
  • User interaction: none
  • Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

  • CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
  • FIRST EPSS (model of 2026-10-26): 0.43% probability of exploitation activity in the next 30 days; percentile 37.

Timeline

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

  1. CVE.org record CVE-2026-115893 cve.org
  2. NVD entry CVE-2026-115893 nvd.nist.gov

Other references from the CVE record and advisory

  1. github.com github.com
  2. github.com github.com
  3. github.com github.com
  4. github.com github.com
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  7. github.com github.com
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  9. github.com github.com
  10. github.com github.com
  11. github.com github.com
  12. github.com github.com

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