VulnerabilityPublished 12 Sep 2026Updated 23 Oct 2026

CVE-2026-90648: WebAssembly wabt · Unchecked Return Value

Affects WebAssembly wabtSource CVE Database V5

Not known to be exploited · CVSS 7.1 High.

Data as of 28 Oct 2026, 05:12 UTC

CVSS 4.0 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: High
Subsequent system availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Subsequent System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Subsequent System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-7jjw-49wp-pr5h

What to do

Affected software

Product	Affected	Fixed in
WebAssemblywabt	Affected <=1.0.41	Fixed in–
GitHubwabt`pkg:github/wabt`Other threats	Affected <=1.0.41	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, mitigating factors include running on 64-bit Linux with default overcommit settings where the defect does not trigger. Avoid running wasm2c in environments with strict memory limits or on 32-bit platforms where allocation failures are more likely. Monitor vendor channels for updates or patches addressing this issue.

Description

CVE-2026-90648 is a high-severity vulnerability in the wasm2c tool of WebAssembly wabt up to version 1.0.41. It involves an unchecked return value from calloc() in the function wasm_rt_allocate_funcref_table(), which can lead to a sandbox escape on primarily 32-bit platforms. When allocation fails, the funcref table's data pointer is left NULL but size remains nonzero, causing bounds checks to pass incorrectly and allowing arbitrary memory read/write and code execution in the host process. This affects sandboxing boundaries used by RLBox and WasmBoxC, including Firefox components that use wasm2c for untrusted input containment. Exploitation requires specific memory pressure conditions or restrictive memory overcommit settings. The vulnerability does not trigger on 64-bit Linux with default overcommit settings.

Impact

Successful exploitation results in a full sandbox escape from wasm2c, enabling arbitrary read and write access to host process memory and arbitrary code execution. This undermines the isolation guarantees provided by wasm2c, potentially compromising applications that rely on it for sandboxing untrusted code, including Firefox components that use wasm2c to sandbox font, media, and XML input libraries. The vulnerability is conditional on allocation failure scenarios, which are more likely on 32-bit hosts or under memory pressure with restrictive overcommit settings. On 64-bit Linux with default memory overcommit, the vulnerability is not triggered.

Summary

The vulnerability in wasm2c (WebAssembly wabt <=1.0.41) is due to failure to check the return value of calloc() in wasm_rt_allocate_funcref_table(). On allocation failure, the funcref table's data pointer remains NULL while the size field retains the guest-declared element count. This causes bounds checks to pass erroneously, allowing out-of-bounds accesses to resolve to absolute host memory addresses. Through table.get, table.set, and call_indirect instructions, an attacker can achieve arbitrary read/write and code execution in the host process, effectively escaping the sandbox. This defect primarily affects 32-bit platforms or environments with strict memory limits (e.g., RLIMIT_AS, vm.overcommit_memory=2). The issue was introduced in commit ab9e0b55 (PR #813).

CWE-252Unchecked Return Value (opens in a new tab)
Base weaknessLikelihood of exploit: LowOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Implementation
Ensure that you account for all possible return values from the function.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 23:20 UTC

WeaknessesCWE-252

Technical details

References

Community reviews

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