CVE-2023-27477

wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's code generation backend, Cranelift, has a bug on x86_64 platforms for the WebAssembly `i8x16.select` instruction which will produce the wrong results when the same operand is provided to the instruction and some of the selected indices are greater than 16. There is an off-by-one error in the calculation of the mask to the `pshufb` instruction which causes incorrect results to be returned if lanes are selected from the second vector. This codegen bug has been fixed in Wasmtiem 6.0.1, 5.0.1, and 4.0.1. Users are recommended to upgrade to these updated versions. If upgrading is not an option for you at this time, you can avoid this miscompilation by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other platforms such as AArch64 and s390x are not affected.

Published: 2023-03-08 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-27477 is rated Low Risk (28.5/100): CVSS Low severity, with low exploitation likelihood (EPSS 0.62%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-27477

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.30% 0.62% +0.33%
2 2026-06-10 0.47% 0.30% -0.18%
3 2026-03-26 — 0.47% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-27477

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.1 3.1 LOW
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 1.6 1.4 [email protected]
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 1.4 [email protected]

Weakness enumeration for CVE-2023-27477

GitHub Security Advisory for CVE-2023-27477

GHSA-xm67-587q-r2vw · Severity: low · Ecosystem: rust — wasmtime vulnerable to miscompilation of `i8x16.select` with the same inputs on x86_64

OS Trackers for CVE-2023-27477

vendor priority summary link
debian unimportant CVE-2023-27477 unimportant priority: Debian including 1 source packages (rust-wasmtime), 3 status rows across 3 suites (forky, sid, trixie): resolved 3. https://security-tracker.debian.org/tracker/CVE-2023-27477

Affected software / configurations for CVE-2023-27477

Vendor Product Version Raw CPE
bytecodealliance cranelift-codegen >= 0.84.0, < 0.91.1 cpe:2.3:a:bytecodealliance:cranelift-codegen:*:*:*:*:*:rust:*:*
bytecodealliance cranelift-codegen 0.92.0 cpe:2.3:a:bytecodealliance:cranelift-codegen:0.92.0:*:*:*:*:rust:*:*
bytecodealliance cranelift-codegen 0.93.0 cpe:2.3:a:bytecodealliance:cranelift-codegen:0.93.0:*:*:*:*:rust:*:*
bytecodealliance wasmtime >= 0.37.0, < 4.0.1 cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:*
bytecodealliance wasmtime 5.0.0 cpe:2.3:a:bytecodealliance:wasmtime:5.0.0:*:*:*:*:rust:*:*
bytecodealliance wasmtime 6.0.0 cpe:2.3:a:bytecodealliance:wasmtime:6.0.0:*:*:*:*:rust:*:*

References for CVE-2023-27477

cvelogic Threat Intelligence