Vulnerability in js-toml (CVE-2026-50029)
Summary
Vulnerability in js-toml (CVE-2026-50029). Risk of unauthorized operations or information disclosure. Exploitable via false. Mitigation: upgrade to 1.1.2 or later.
Original description
The description as published by the source.
js-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with if (object[key]) instead of if (key in object). When the prior value is a falsy primitive — false, 0, 0n, 0.0, -0, or "" — the duplicate-key branch is skipped and the value is silently overwritten by a later sub-table, dotted-key sub-table, or array-of-tables sharing the same name. Per the TOML 1.0.0 spec ("Defining a key multiple times is invalid"; "You cannot define any key or table more than once"), this should be a parse error. The result is structural type confusion of attacker-named keys in the value returned by load(). A boolean-typed false (or numeric 0) becomes a truthy object. Host applications that gate behavior on if (config.flag), if (!user.banned), if (config.allowDelete), or if (config.publicMode) will silently take the truthy branch. This is distinct from GHSA-65fc-cr5f-v7r2 (the 1.0.2 prototype-pollution fix). Object.prototype is not polluted. The Object.create(null) mitigation from 1.0.2 is intact; the bug here is in the duplicate-key state machine, not in container construction. Version 1.1.2 patches the incorrect comparison.
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-2026-50029 has been found in js-toml.
Attackers can target a specific entry point like false over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade js-toml to 1.1.2 or later.
If unsure, ask your IT team or search "js-toml CVE-2026-50029" on the vendor's site.
CVE-2026-50029 (js-toml) — CWE-697 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: false / Object.prototype / Interpreter.tryCreatingObject / Interpreter.getOrCreateArray
Patched: 1.1.2 — 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-697) exists in js-toml. Attackers reach the vulnerable code path via false without authentication.
Check the vendor advisory for the affected versions of js-toml. Attack surface: false / Object.prototype / Interpreter.tryCreatingObject / Interpreter.getOrCreateArray.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.1.2.
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 'js-toml' . 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
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1Identify exposure identify
grep -r 'js-toml' . | 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
js-toml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 js-toml to 1.1.2ステージング環境で 1.1.2 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。
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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。
Affected packages
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com