DeepmergeTS has stack exhaustion when merging recursive object graphs

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

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 · score source

EPSS

• CVE-2026-40345: 0.52% estimated exploitation activity in the next 30 days; percentile 44.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary deepmerge() and deepmergeInto() can be crashed with a crafted recursive object graph. When both merged values contain self-references at the same property path, the library recurses until Node throws RangeError: Maximum call stack size exceeded. Details Record merging is implemented recursively. For each enumerable key, the library collects the values from every input object and immediately calls the same merge routine on that property. There is no visited-object tracking, pair tracking, or cycle detection in that recursion. As a result, if two merged records both point back to themselves through the same key path, the merge logic keeps revisiting the same object pair forever. This is reachable through the real public API: deepmerge(...) deepmergeCustom(...)(...) deepmergeInto(target, ...) deepmergeIntoCustom(...)(target, ...) The issue only occurs when recursive object graphs are supplied. Plain JSON alone does not create this condition. PoC Impact Applications that pass…

Published by the source

17 Aug 2026, 13:32 UTC

Last modified by the source

17 Aug 2026, 13:32 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ggr8-5vv4-36mx

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# Patch Next advisory brief: CVE-2026-40345

Advisory: DeepmergeTS has stack exhaustion when merging recursive object graphs
IDs: CVE-2026-40345, GHSA-ggr8-5vv4-36mx
Record: https://patchnext.com/advisories/cve-2026-40345 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: deepmerge-ts 8.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm deepmerge-ts: affected < 8.0.0; fixed in 8.0.0

## Suggested inspection (read-only)
- `npm ls deepmerge-ts --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on deepmerge-ts.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-ggr8-5vv4-36mx (GitHub-reviewed advisory GHSA-ggr8-5vv4-36mx lists affected ranges: npm deepmerge-ts >=0 <8.0.0)

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