CVE-2026-40345 deepmerge-ts: Stack exhaustion when merging recursive object graphs
Attackers can crash applications by supplying recursive object graphs to deepmerge-ts, causing stack exhaustion and process termination.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40345?
CVE-2026-40345 is a high-severity denial of service vulnerability in RebeccaStevens deepmerge-ts, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
deepmerge-ts is a typescript library providing functionality to deep merging of javascript objects. Prior to 8.0.0, the deepmerge, deepmergeCustom, deepmergeInto, and deepmergeIntoCustom APIs do not track visited objects or object pairs when recursively merging records. When two input values contain self-references at the same property path, the merge logic repeatedly revisits the same pair until Node.js raises RangeError: Maximum call stack size exceeded. Applications that merge attacker-controlled recursive object graphs can synchronously crash the affected process or cause repeated worker restarts. Plain JSON input alone cannot create the recursive graph required to trigger the issue. This issue is fixed in version 8.0.0.
Weakness: CWE-674
Which versions are affected by CVE-2026-40345?
2 open source packages ship an affected version, including deepmerge-ts.
| Package | Affected | Fixed in |
|---|---|---|
deepmerge-ts npm | All versions | 8.0.0 |
deepmerge-ts npm | All versions | 8.0.0 |
How do I fix CVE-2026-40345?
Upgrade deepmerge-ts to 8.0.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-40345 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40345 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as CLEANSTART-2026-ML15245, CLSA-2026-1790420043, CLSA-2026-1790609747, CLSA-2026-1790870726, CLSA-2026-1792476546, ECHO-097f-3757-c05a and 1 more.