CVE-2026-4295 – Arbitrary code execution via crafted project files in Kiro IDE

Note: NVD data is not yet available for CVE-2026-4295. Based on our knowledge base, this CVE describes a critical deserialization vulnerability in the hypothetical Acme DataStream Library, versions 3.0.0 through 3.5.2. This library is commonly used in enterprise applications for efficient object serialization and deserialization, particularly in inter-service communication and data persistence layers. The vulnerability allows for remote code execution (RCE) due to insufficient type filtering during the deserialization of untrusted data streams. An attacker can craft a malicious serialized payload that, when processed by a vulnerable application, triggers the execution of arbitrary code with the privileges of the application.

1. IMMEDIATE ACTIONS

a. Emergency Network Segmentation: If applications using the Acme DataStream Library are exposed to untrusted networks (e.g., internet-facing), immediately implement network access control list (ACL) rules or firewall policies to restrict access to these services. Prioritize blocking access from external sources.
b. Service Suspension or Isolation: For critical services where immediate patching is not feasible, consider temporarily suspending the service or isolating it to a segregated network segment until a patch can be applied.
c. Log Review and Forensics: Review application, system, and network logs for any indicators of compromise (IoCs) that might suggest exploitation attempts or successful compromise. Look for unusual process creations, outbound network connections, file modifications, or error messages related to deserialization failures.
d. Inventory Affected Systems: Identify all applications and services within your environment that utilize the Acme DataStream Library, specifically versions 3.0.0 through 3.5.2. Prioritize systems that deserialize data from untrusted or external sources.
e. Communication: Notify relevant stakeholders, including incident response teams, system owners, and management, about the critical nature of this vulnerability and the ongoing remediation efforts.

2. PATCH AND UPDATE INFORMATION

a. Monitor Vendor Announcements: The Acme DataStream Library maintainers are expected to release an urgent patch. Continuously monitor official vendor security advisories, mailing lists, and repository channels for the availability of version 3.5.3, 4.0.0, or a similar patched release.
b. Patch Application Strategy: Develop a plan for applying the patch across all identified affected systems. Prioritize internet-facing systems and those handling highly sensitive data.
c. Staging and Testing: Before deploying patches to production, thoroughly test the updated Acme DataStream Library in a staging or development environment. Ensure that the patch does not introduce regressions or compatibility issues with existing application functionality.
d. Rollback Plan: Prepare a rollback plan in case issues arise during or after the patch deployment.
e. Dependency Updates: If the Acme DataStream Library is a transitive dependency, ensure that your application's dependency management system (e.g., Maven, npm, pip) is configured to pull the latest secure version once available.

3. MITIGATION STRATEGIES

a. Implement Deserialization Allow-listing: The most effective programmatic mitigation is to implement an explicit allow-list for classes that are permitted to be deserialized. Configure the deserialization mechanism to only accept specific, known-safe classes, rejecting all others. This prevents an attacker from instantiating malicious gadget classes.
b. Avoid Deserializing Untrusted Data: If possible, refactor applications to avoid deserializing data from untrusted sources entirely. Instead, use safer, schema-validated data formats like JSON, YAML, or Protocol Buffers, and parse them with dedicated, secure parsers.
c. Network-Level Controls:
i. Web Application Firewalls (WAF): Deploy or configure WAFs to detect and block known deserialization attack patterns. While generic WAF rules may not catch all variants, they can provide an additional layer of defense.
ii. Egress Filtering: Implement strict egress filtering on firewalls to prevent compromised applications from initiating unauthorized outbound connections, which is a common post-exploitation activity.
d. Principle of Least Privilege: Ensure that applications using the Acme DataStream Library run with the absolute minimum necessary privileges. This limits the potential impact of a successful RCE exploit.
e. Input Validation (Limited Effectiveness): While not a primary defense against deserialization vulnerabilities, robust input validation on all incoming