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CVE-2026-54786· NVD / CVE Program· CNA GitHub_M

Wasmtime: Leak in WASIp1 `fd_renumber` implementation

Wasmtime is a runtime for WebAssembly. All versions prior to 24.0.10; versions 25.0.0 through those before 36.0.11; versions 37.0.0 through those before 44.0.3; and versions 45.0.0 and 45.0.1 contain a native implementation of WASIp1 which suffers from a leak in the fd_renumber function where the file descriptor being renumbered to is not properly closed. Wasmtime's implementation erroneously only updated the table of descriptors for WASIp1 and didn't update the underlying table of descriptors used by the host. This behavior means that while fd_renumber works correctly from a guest's perspective it ends up leaking resources in the host that aren't cleaned up until the corresponding Store is destroyed. In a loop, guests can use fd_renumber to cause hosts to exhaust both resources and file descriptors. This bug only affects the native implementation of WASIp1, meaning that only runtimes which load core wasm modules and expose fd_renumber are affected. Runtimes are additionally only affected if they expose the ability to acquire a file descriptor, such as opening a file. For runtimes that deny access to files they are unaffected. This issue has been fixed in versions 24.0.10, 36.0.11, 44.0.3, and 45.0.2.

LowCVSS 2.3 · v4.0—No exploit Fix available
Published
Jul 1, 2026
Updated
Jul 2, 2026
EPSS
0.4% · 29th percentile
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Report tools

JSON

Action score

9

Monitor

Low priority for now.

CVSS
9 / 40 · 2.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
2.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Affected systems

VendorProduct
bytecodealliancewasmtime

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • bytecodealliance wasmtimebefore 24.0.10
  • bytecodealliance wasmtime25.0.0 and later · before 36.0.11
  • bytecodealliance wasmtime37.0.0 and later · before 44.0.3
  • bytecodealliance wasmtime45.0.0 and later · before 45.0.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • bytecodealliance wasmtime

    • < 24.0.10, >= 25.0.0, < 36.0.11, >= 37.0.0, < 44.0.3, >= 45.0.0, < 45.0.2affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
crates.iowasmtime-wasifrom 0.0.0-0 · before 24.0.1024.0.10
crates.iowasmtime-wasifrom 25.0.0 · before 36.0.1136.0.11
crates.iowasmtime-wasifrom 37.0.0 · before 44.0.344.0.3
crates.iowasmtime-wasifrom 45.0.0 · before 45.0.245.0.2
crates.iowasmtime-wasibefore 24.0.1024.0.10
Debian:13rust-wasmtimeall versions—
Debian:14rust-wasmtimebefore 36.0.11+dfsg-136.0.11+dfsg-1

Same product

bytecodealliance: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-39394wasmtime_trap_code C API function has out of bounds write vulnerability
    39Monitor
  • CVE-2022-24791Use after free in Wasmtime
    39Monitor
  • CVE-2026-34987Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access
    36Monitor
  • CVE-2026-34971Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift
    36Monitor
  • CVE-2023-30624Wasmtime has Undefined Behavior in Rust runtime functions
    35Monitor
  • CVE-2022-39393Wasmtime vulnerable to data leakage between instances in the pooling allocator
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
crates.io:wasmtime-wasi24.0.10Package registry (OSV)
crates.io:wasmtime-wasi36.0.11Package registry (OSV)
crates.io:wasmtime-wasi44.0.3Package registry (OSV)
crates.io:wasmtime-wasi45.0.2Package registry (OSV)
debian:rust-wasmtime36.0.11+dfsg-1 · Debian:14Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-27204127 days apartWasmtime WASI implementations are vulnerable to guest-controlled resource exhaustion
    27Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
X

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/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

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
function expand(node) {  return node.children.map(expand);}

Fixed

ts
const MAX_DEPTH = 32;function expand(node, depth = 0) {  if (depth > MAX_DEPTH) throw new Error("too deep");  return node.children.map((c) => expand(c, depth + 1));}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records