What’s Vulnerable › Vulnerabilities

CVE-2026-25641: SandboxJS has a sandbox escape via TOCTOU bug on keys in property accesses

• Severity: critical (CVSS 9.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-02-06 · updated 2026-06-17
• Weakness: CWE-367

Description

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.29, there is a sandbox escape vulnerability due to a mismatch between the key on which the validation is performed and the key used for accessing properties. Even though the key used in property accesses is annotated as string, this is never enforced. So, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using hasOwnProperty(key) and a different one for when the key is used for the actual property access. This vulnerability is fixed in 0.8.29.

Affected products

• nyariv SandboxJS: before 0.8.29 — fixed in 0.8.29

How to fix

Upgrade to a fixed version: nyariv SandboxJS 0.8.29. Check the vendor advisory for mitigations.

References

• https://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304
• https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3
• https://github.com/nyariv/SandboxJS/security/advisories/GHSA-7x3h-rm86-3342
• https://github.com/nyariv/SandboxJS/security/advisories/GHSA-7x3h-rm86-3342

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