CVE-2026-34043

Impact

What kind of vulnerability is it?

It is a Denial of Service (DoS) vulnerability caused by CPU exhaustion. When serializing a specially crafted "array-like" object (an object that inherits from Array.prototype but has a very large length property), the process enters an intensive loop that consumes 100% CPU and hangs indefinitely.

Who is impacted?

Applications that use serialize-javascript to serialize untrusted or user-controlled objects are at risk. While direct exploitation is difficult, it becomes a high-priority threat if the application is also vulnerable to Prototype Pollution or handles untrusted data via YAML Deserialization, as these could be used to inject the malicious object.

Patches

Has the problem been patched?

Yes, the issue has been patched by replacing instanceof Array checks with Array.isArray() and using Object.keys() for sparse array detection.

What versions should users upgrade to?

Users should upgrade to v7.0.5 or later.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

There is no direct code-level workaround within the library itself. However, users can mitigate the risk by:

• Validating and sanitizing all input before passing it to the serialize() function.
• Ensuring the environment is protected against Prototype Pollution.
• Upgrading to v7.0.5 as soon as possible.

Acknowledgements

Serialize JavaScript thanks Tomer Aberbach (@TomerAberbach) for discovering and privately disclosing this issue.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Serialize JavaScript to a superset of JSON that includes regular expressions and functions. Prior to version 7.0.5, there is a Denial of Service (DoS) vulnerability caused by CPU exhaustion. When serializing a specially crafted "array-like" object (an object that inherits from Array.prototype but has a very large length property), the process enters an intensive loop that consumes 100% CPU and hangs indefinitely. This issue has been patched in version 7.0.5.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

TuxCare rebuilt formidable to address 4 CVEs. Fixed in 2.1.2-tuxcare.1.

TuxCare rebuilt serialize-javascript to address 3 CVEs. Fixed in 2.1.2-tuxcare.1.

TuxCare rebuilt serialize-javascript to address 1 CVE. Fixed in 6.0.2-tuxcare.2.

TuxCare rebuilt serialize-javascript to address 1 CVE. Fixed in 5.0.1-tuxcare.2.

TuxCare rebuilt serialize-javascript to address 1 CVE. Fixed in 7.0.4-tuxcare.1.

TuxCare rebuilt serialize-javascript to address 1 CVE. Fixed in 7.0.2-tuxcare.2.

Root has patched CVE-2026-34043 in the @rootio/serialize-javascript package for Root:npm. Multiple fixed versions available.