Vulnerability in deepmerge-ts (CVE-2026-40345)
Summary
Vulnerability in deepmerge-ts (CVE-2026-40345). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 8.0.0 or later.
Original description
The description as published by the source.
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
import { deepmerge, deepmergeInto } from "deepmerge-ts";
const left = {};
left.self = left;
const right = {};
right.self = right;
try {
deepmerge(left, right);
} catch (error) {
console.log(error.name, error.message);
// Expected: the merge should reject or safely handle recursive input without exhausting the stack.
// Vulnerable behavior: RangeError Maximum call stack size exceeded
}
const target = {};
target.self = target;
const source = {};
source.self = source;
tr…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-40345 has been found in deepmerge-ts.
Risk of unauthorized operations or information disclosure.
What to do: upgrade deepmerge-ts to 8.0.0 or later.
If unsure, ask your IT team or search "deepmerge-ts CVE-2026-40345" on the vendor's site.
CVE-2026-40345 (deepmerge-ts) — CWE-674
Patched: 8.0.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-674) exists in deepmerge-ts.
Check the vendor advisory for the affected versions of deepmerge-ts.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 8.0.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'deepmerge-ts' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'deepmerge-ts' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
deepmerge-tsを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade deepmerge-ts to 8.0.0ステージング環境で 8.0.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。