UBUNTU-CVE-2026-34987

See a problem?
Please try reporting it to the source first.
Source
https://ubuntu.com/security/CVE-2026-34987
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-34987
Upstream
Published
2026-04-09T19:16:00Z
Modified
2026-05-20T16:12:55.194307955Z
Severity
  • 9.0 (Critical) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H CVSS Calculator
  • 9.9 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

References

Affected packages

Ubuntu:24.04:LTS / rust-wasmtime

Package

Name
rust-wasmtime
Purl
pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

10.*
10.0.1+dfsg-7
15.*
15.0.1+dfsg-4
16.*
16.0.0+dfsg-2
16.0.0+dfsg-3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "0.103.0+16.0.0+dfsg-3",
            "binary_name": "librust-cranelift-dev"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"

Ubuntu:25.10 / rust-wasmtime

Package

Name
rust-wasmtime
Purl
pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

26.*
26.0.1+dfsg-3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "0.113.1+26.0.1+dfsg-3",
            "binary_name": "librust-cranelift-dev"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"

Ubuntu:26.04:LTS / rust-wasmtime

Package

Name
rust-wasmtime
Purl
pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

26.*
26.0.1+dfsg-3
26.0.1+dfsg-4
28.*
28.0.1+dfsg-3
29.*
29.0.1+dfsg-5
36.*
36.0.5+dfsg-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "0.123.5+36.0.5+dfsg-1",
            "binary_name": "librust-cranelift-dev"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"