# 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.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** CLEANSTART-2026-ML15245, CLSA-2026-1790420043, CLSA-2026-1790609747, CLSA-2026-1790870726, CLSA-2026-1792476546, ECHO-097f-3757-c05a, GHSA-ggr8-5vv4-36mx

## 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 (Uncontrolled Recursion)

## Which versions are affected by CVE-2026-40345?

2 open source packages ship an affected version, including deepmerge-ts.


| Package | Ecosystem | 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.

## 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:

- A poc and write-up for CVE-2026-40345 (github_poc): https://github.com/Jvr2022/CVE-2026-40345

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40345 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40345 exists.

Affected packages and fixed versions:
- deepmerge-ts (npm): affected all versions; fixed in 8.0.0
- deepmerge-ts (npm): affected all versions; fixed in 8.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40345/ (Markdown: https://insights.sbomify.com/CVE-2026-40345/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40345
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40345
- OSV: https://osv.dev/vulnerability/CVE-2026-40345

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-40345/
Summaries are generated and may contain mistakes; the official description above is the record.