CVE-2026-126410
Wasmtime 48.0.0 before 48.0.8 TOCTOU UDP Send Policy Bypass via wasip3 Sockets
CVE-2026-126410 is a medium vulnerability (CVSS 5.3) 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 0.16%, the 5th percentile. Fixed in wasmtime-wasi 48.0.8.
- Severity
- 5.3 MediumCVSS 4.0, CVE List
- Exploit chance
- 0.16%EPSS, 5th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
48.0.8wasmtime-wasi +3 more
Description
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
wasmtime-wasicrates.io | 48.0.0 up to 48.0.8, 49.0.0 up to 49.0.5, 50.0.0 up to 50.0.1 | 48.0.849.0.550.0.1 |
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 48.0.0 before 48.0.8 TOCTOU UDP Send Policy Bypass via wasip3 Sockets
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
CVE-2026-126410- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N - CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N - Weakness
- CWE-367
- Updated
- 2026-11-13
EUVDEUVD-2026-125033
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
EUVD-2026-125033- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N - Updated
- 2026-11-13
GitHub AdvisoriesGHSA-55h5-m765-f99r
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0...
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
GHSA-55h5-m765-f99r- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/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
- 6.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N - Weakness
- CWE-367
- Updated
- 2026-11-13
NVD
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
CVE-2026-126410- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/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
- 6.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N - Weakness
- CWE-367
- Updated
- 2026-11-13
OSV
Wasmtime 48.0.0 before 48.0.8 TOCTOU UDP Send Policy Bypass via wasip3 Sockets
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
CVE-2026-126410- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N - Weakness
- CWE-367
- Updated
- 2026-11-14
OSVRUSTSEC-2026-0420
wasip3 UDP `send` can deliver a datagram to an address only allowed for receiving
This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hmmr-87qq-258j For more information see the GitHub-hosted security advisory.
- Record
RUSTSEC-2026-0420- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-14
OSVUBUNTU-CVE-2026-126410
Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socket_addr_check send restrictions. A malicious guest can race udp-socket.send against udp-socket.connect to deliver attacker-controlled datagrams to addresses the policy permits only for receiving.
- Record
UBUNTU-CVE-2026-126410- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N - CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-13
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, facts, published, references | OSV | |
| affected, aliases, published, references | 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-hmmr-87qq-258j
vulncheck.com/advisories/wasmtime-48.0.0-before-48.0.8-toctou-udp-send-policy-bypass-via-wasip3-sockets
nvd.nist.gov/vuln/detail/CVE-2026-126410
crates.io/crates/wasmtime-wasi