CVE-2026-126407
Wasmtime before 36.0.20 Denial of Service via Borrowed Resource Transfer
CVE-2026-126407 is a medium vulnerability (CVSS 5.9) in Bytecodealliance Wasmtime, published October 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.31%, the 24th percentile. Fixed in wasmtime 36.0.20.
- Severity
- 5.9 MediumCVSS 4.0, CVE List
- Exploit chance
- 0.31%EPSS, 24th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
36.0.20wasmtime +3 more
Description
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- Passive
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
wasmtimecrates.io | 0.0.0-0 up to 36.0.20, 37.0.0 up to 48.0.8, 49.0.0 up to 49.0.5, 50.0.0 up to 50.0.1 | 36.0.2048.0.849.0.550.0.1 |
rust-wasmtimeUbuntu:24.04:LTS | All versions, plus listed versions 10.0.1+dfsg-715.0.1+dfsg-416.0.0+dfsg-216.0.0+dfsg-3 | None known |
rust-wasmtimeUbuntu:26.10 | All versions, plus listed versions 36.0.5+dfsg-136.0.13+dfsg-1 | None known |
rust-wasmtimeUbuntu:26.04:LTS | All versions, plus listed versions 26.0.1+dfsg-326.0.1+dfsg-428.0.1+dfsg-329.0.1+dfsg-536.0.5+dfsg-1 | None known |
What each source reports
CVE List Score used
Wasmtime before 36.0.20 Denial of Service via Borrowed Resource Transfer
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
CVE-2026-126407- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-13
EUVDEUVD-2026-125036
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
EUVD-2026-125036- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-13
GitHub AdvisoriesGHSA-2gjh-4jcm-q34v
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1...
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
GHSA-2gjh-4jcm-q34v- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/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 - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-13
NVD
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
CVE-2026-126407- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/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 - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-13
OSV
Wasmtime before 36.0.20 Denial of Service via Borrowed Resource Transfer
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
CVE-2026-126407- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-770
- Updated
- 2026-11-14
OSVUBUNTU-CVE-2026-126407
Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed resources to consume arbitrary host memory, causing denial of service.
- Record
UBUNTU-CVE-2026-126407- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-13
OSVRUSTSEC-2026-0424No score
Unchecked memory usage in transferring borrowed resources between components
This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-6fr9-xmw9-5352 For more information see the GitHub-hosted security advisory.
- Record
RUSTSEC-2026-0424- Updated
- 2026-11-14
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, facts, published, references | OSV | |
| affected, aliases, published, references | NVD, OSV | |
| published | EUVD | |
| published | EUVD | |
| aliases, references | GitHub Advisories, NVD | |
| aliases, published | EUVD | |
| first indexed | CVE List | |
| first indexed | OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
References
github.com/bytecodealliance/wasmtime/security/advisories/GHSA-6fr9-xmw9-5352
vulncheck.com/advisories/wasmtime-before-36.0.20-denial-of-service-via-borrowed-resource-transfer
nvd.nist.gov/vuln/detail/CVE-2026-126407
crates.io/crates/wasmtime