CriticalPublic exploit

SandboxJS sandbox escape via hasOwnProperty shadowing (prototype whitelist bypass)

IdentifiersCVE-2026-25586CWE-1321

In @nyariv/sandboxjs (SandboxJS) prior to 0.8.29, the sandbox’s property-access path relies on hasOwnProperty checks in a way that can be subverted by an attacker who shadows/replaces hasOwnProperty on a sandboxed object. By forcing the attacker-controlled hasOwnProperty to return true, the library’s prototype whitelist enforcement is effectively bypassed, permitting access to normally blocked prototype properties such as proto. This enables host-side Object.prototype pollution and can create persistent, cross-sandbox impact. Fixed in 0.8.29.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation results in a sandbox escape primitive that allows access to blocked prototype properties (e.g., proto) and enables host Object.prototype pollution. Consequences include persistent cross-sandbox compromise, logic/authorization bypass in host code that consumes polluted properties, denial of service via prototype method/property override, and potential RCE when combined with host-side gadgets that act on attacker-influenced properties (e.g., executing commands/paths/options sourced from polluted objects).

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible: (1) avoid executing untrusted code in SandboxJS; (2) run the sandbox in a separate, tightly confined OS process/container/VM (e.g., seccomp/AppArmor, minimal privileges, no sensitive env vars, read-only FS, no host IPC); (3) harden host code against prototype pollution by using Object.create(null) for option/parameter bags, validating inputs, and performing own-property checks via Object.prototype.hasOwnProperty.call(obj, key) rather than obj.hasOwnProperty(key).

Remediation

Patch, then assume compromise.

Upgrade @nyariv/sandboxjs to 0.8.29 or later, which fixes the prototype whitelist bypass.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Nyariv@Nyariv/Sandboxjsapplication

NyarivSandboxjsapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

7 SOURCESView more in app

security online infoNews

Feb 9, 2026

Code Red: 4 Critical SandboxJS Flaws (CVSS 10.0) Allow Host Takeover

SandboxJS sandbox escape / host environment compromise via host prototype pollution by shadowing hasOwnProperty to bypass whitelist checks and reach sensitive prototypes (e.g., __proto__).

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity6

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-25586

NVD

nvd.nist.gov/vuln/detail/CVE-2026-25586

MITRE CWE · CWE-1321

cwe.mitre.org

Patch

github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3

Vendor Advisory

github.com/nyariv/SandboxJS/security/advisories/GHSA-jjpw-65fv-8g48