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Fencer Vulns
high 8.2

CVE-2026-63376 json

toml-node: Prototype Pollution Leads to `Object.prototype` Corruption via `__proto__` Key-Path Desynchronization

published 2026-09-03 2 mo ago modified 2026-09-09 1 mo ago also GHSA-v5mp-jgw5-2x6j , EUVD-2026-70738

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

toml-node is a TOML parser for Node.js and the browser. Prior to 4.1.2, toml.parse() in lib/compiler.js can be tricked by a table path such as a.b.y.__proto__.__proto__, allowing traversal from a scalar value into Number.prototype and Object.prototype. The currentPath tracking value uses both arrays and strings, so valueAssignments records a comma-joined path such as a,b.y while deepRef checks the dot-joined path a.b.y, allowing the duplicate-key guard to miss and attacker-controlled keys to be written to Object.prototype. A table-array prefix-clearing path in addTableArray can also erase guard state before the same __proto__ traversal. Injected properties become visible throughout the Node.js process and can cause denial of service, logic or authorization bypass, or code execution when an application contains a suitable gadget. This issue is fixed in version 4.1.2.

Patch / fix

  • npm toml 4.1.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63376 updated cvss 3.7

toml-node: toml-node: Arbitrary Code Execution via Prototype Pollution in TOML Parsing

  • Red Hat Enterprise Linux 10 cockpit-image-builder
    affected: workaround, no fix available “No mitigation is available for this vulnerability.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.68% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/BinaryMuse/toml-node/security/advisories/GHSA-v5mp-jgw5-2x6j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
GitHub 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Affected packages

ecosystem package affected fixed in
npm toml
<4.1.2
4.1.2

Affected products

  • BinaryMuse toml-node

Classification

Weakness
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.