CVE-2026-40345 RebeccaStevens CVE debrief

Who should care

Developers and administrators using deepmerge-ts versions prior to 8.0.0 should assess exposure and prioritize remediation. This includes reviewing the affected versions, verifying if applications merge attacker-controlled recursive object graphs, and updating to version 8.0.0 or later. Security teams and vulnerability management teams should also be aware of the potential impact and take necessary actions to mitigate the vulnerability.

Why it matters

CVE-2026-40345 is a high-severity vulnerability in the deepmerge-ts library that can cause synchronous crashes or repeated worker restarts. Developers and administrators using affected versions should assess exposure and prioritize remediation.

• Synchronous process crash or repeated worker restarts
• Potential for denial-of-service (DoS) attacks
• Need for verification of affected versions and exposure
• Remediation priority for applications using deepmerge-ts versions prior to 8.0.0

Technical summary

The deepmerge-ts library, prior to version 8.0.0, does not track visited objects or object pairs when recursively merging records. This oversight can lead to a RangeError: Maximum call stack size exceeded when merging attacker-controlled recursive object graphs. The vulnerability is caused by the deepmerge, deepmergeCustom, deepmergeInto, and deepmergeIntoCustom APIs not tracking visited objects or object pairs during recursive merging. Applications that merge attacker-controlled recursive object graphs can synchronously crash the affected process or cause repeated worker restarts.

Defensive priority

High

Recommended defensive actions

• Assess exposure and prioritize remediation for applications using deepmerge-ts versions prior to 8.0.0
• Verify if applications merge attacker-controlled recursive object graphs
• Update to version 8.0.0 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by the deepmerge, deepmergeCustom, deepmergeInto, and deepmergeIntoCustom APIs not tracking visited objects or object pairs when recursively merging records. This can lead to a RangeError: Maximum call stack size exceeded.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.