6.5

CVE-2026-34945: bytecodealliance wasmtime

CVSS: 6.5v3.1MediumAnalyzed
AliasesUBUNTU-CVE-2026-34945DEBIAN-CVE-2026-34945CGA-5ccm-x568-6m8r
Published 09-04-2026Last modified 10-04-2026
Open JSON

Vulnerability summary

CVE-2026-34945 is a medium (CVSS 6.5) vulnerability in bytecodealliance wasmtime. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 30.4% of scored vulnerabilities.

Overall risk
26/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.38%
0%100%
Low · +0.06 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-RR57-4C3V-MQV3

Timeline

  1. 09-04-2026
    PublishedVulnerability first disclosed.
  2. 10-04-2026
    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 contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size instruction. This bug could lead to disclosing data on the host's stack to WebAssembly guests. The host's stack can possibly contain sensitive data related to other host-originating operations which is not intended to be disclosed to guests. This bug specifically arose from a mistake where the return value of table.size was statically typed as a 32-bit integer, as opposed to consulting the table's index type to see how large the returned register could be. When combined with details about Wnich's ABI, such as multi-value returns, this can be combined to read stack data from the host, within a guest. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

CVSS metrics

9 scores · 7 sources · 2 versions

EPSS trend

Probability

0.38%

Chance of exploitation in the next 30 days

Percentile

30%

Versus all other CVEs

30-day change

+0.06 pp

From 0.32% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.38%

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, < 43.0.1
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
Opensuse1 product
  • tree-sitter&distro=openSUSE Tumbleweed< 0.26.8-1.1
Ubuntu1 product
  • rust-wasmtimeAll versions (No fix recorded)

7 vendors · 15 products

References

11 links
Show all 11 references