7.5

CVE-2026-35186: bytecodealliance wasmtime

CVSS: 7.5v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-35186DEBIAN-CVE-2026-35186CGA-2pc3-5w4w-qcv4
Published 09-04-2026Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2026-35186 is a high (CVSS 7.5) vulnerability in bytecodealliance wasmtime. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.8% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.16 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1 · Related 2
OPENSUSE-SU-2026:10715-1CGA-3QCH-4HWR-G7QM

Timeline

  1. 09-04-2026
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

Description

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler backend contains a bug where translating the table.grow operator causes the result to be incorrectly typed. For 32-bit tables this means that the result of the operator, internally in Winch, is tagged as a 64-bit value instead of a 32-bit value. This invalid internal representation of Winch's compiler state compounds into further issues depending on how the value is consumed. The primary consequence of this bug is that bytes in the host's address space can be stored/read from. This is only applicable to the 16 bytes before linear memory, however, as the only significant return value of table.grow that can be misinterpreted is -1. The bytes before linear memory are, by default, unmapped memory. Wasmtime will detect this fault and abort the process, however, because wasm should not be able to access these bytes. Overall this this bug in Winch represents a DoS vector by crashing the host process, a correctness issue within Winch, and a possible leak of up to 16-bytes before linear memory. Wasmtime's default compiler is Cranelift, not Winch, and Wasmtime's default settings are to place guard pages before linear memory. This means that Wasmtime's default configuration is not affected by this issue, and when explicitly choosing Winch Wasmtime's otherwise default configuration leads to a DoS. Disabling guard pages before linear memory is required to possibly leak up to 16-bytes of host data. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

CVSS metrics

10 scores · 7 sources · 2 versions

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

30%

Versus all other CVEs

30-day change

+0.16 pp

From 0.21% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.37%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard5 products
  • washAll versions (No fix recorded)
  • wasmcloud< 2.0.4-r0
  • wizer< 11.0.3-r10
  • yara-x< 1.15.0-r2
  • zed< 0.228.0-r3
Wolfi5 products
  • washAll versions (No fix recorded)
  • wasmcloud< 2.0.4-r0
  • wizer< 11.0.3-r10
  • yara-x< 1.15.0-r2
  • zed< 0.228.0-r3
Bytecodealliance1 product
  • wasmtime≥ 43.0.0, < 44.0.1 | ≥ 25.0.0, < 36.0.7 | ≥ 37.0.0, < 42.0.2 | 43.0.0
Crates.Io1 product
  • wasmtime≥ 25.0.0, < 36.0.7 | ≥ 37.0.0, < 42.0.2 | ≥ 43.0.0, < 43.0.1
Debian1 product
  • rust-wasmtimeAll versions (No fix recorded) | < 36.0.7+dfsg-1
Ubuntu1 product
  • rust-wasmtimeAll versions (No fix recorded)

6 vendors · 14 products

References

10 links