CVE Intelligence
Medium

CVE-2026-115892 — Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type

Wasmtime is a runtime for WebAssembly. From 46.0.0 until 48.0.7 and 49.0.4, lowering a host-created component-model stream or future into a guest can omit a required payload-type check after the value passes through guest code and returns through StreamAny, FutureAny, Val::Stream, Val::Future, or an equivalent typed reader. A malicious guest that controls exported function types or returned values can cause the host to pass the type-erased value to a guest expecting a different payload type, which panics the Wasmtime host. This issue is fixed in versions 48.0.7 and 49.0.4.

Published Oct 23, 2026 · Updated Oct 29, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+6
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.43%
ahead of 38% of scored CVEs · Oct 29, 2026
Affects
Bytecodealliance
Wasmtime
CVSS base
5.7
Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Rust Wasmtime: fixed in version 48.0.7 — github.com (GitHub Security Advisories)
  • Rust Wasmtime: fixed in version 49.0.4 — github.com (GitHub Security Advisories)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Bytecodealliance Wasmtime, Rust Wasmtime).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Bytecodealliance Wasmtime version >= 46.0.0, < 48.0.7version >= 49.0.0, < 49.0.4 Vulnerable CVE Program (cve.org) e CISA ADP
Rust Wasmtime ≥ 46.0.0 and < 48.0.7≥ 49.0.0 and < 49.0.4 Vulnerable GitHub Security Advisories

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Attack requirements
Present
Privileges required
High
User interaction
Passive
Scope
X
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
None
Availability (vulnerable system)
High
Confidentiality (subsequent)
None
Integrity (subsequent)
None
Availability (subsequent)
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.7 CVSS 4.0 Medium — — security-advisories@github.com via NIST National Vulnerability Database
5.7 CVSS 4.0 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/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 (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-248

Other CVEs with this weakness →

EPSS over time FIRST

Oct 24, 2026 → Oct 29, 2026 · 6 reading(s) · max 0.56%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 29, 2026 · CVE Program (cve.org) e CISA ADP
  • Fix documented
    Oct 23, 2026 · GitHub Security Advisories
  • Affected products added · rust/wasmtime
    Oct 23, 2026 · GitHub Security Advisories
  • Affected products added · bytecodealliance/wasmtime
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 23, 2026
  • CVSS changed · 5.7
    Oct 23, 2026 · NIST National Vulnerability Database
  • Source status changed · → Deferred
    Oct 23, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 23, 2026 · NIST National Vulnerability Database
  • CVE published
    Oct 23, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 23, 2026 – Oct 23, 2026
  • 1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

11 on the record

Elsewhere on this site

Bytecodealliance
every CVE for this vendor
CWE-248
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-119140 Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Host Panic via thread.yield 21h
  • CVE-2026-119137 Wasmtime 42.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Stack Overflow via Type Registry 21h
  • CVE-2026-119141 Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Host Panic via realloc 21h
  • CVE-2026-119142 Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Host Panic via call_async Drop 21h
  • CVE-2026-119138 Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Panic After Trap 21h
  • CVE-2026-119143 Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Panic via Zero-Length Stream Writes 21h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-115892 is "Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type", rated Medium. It affects Wasmtime (Bytecodealliance); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.7 describes technical severity. EPSS 0.43% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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