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high SEVERITY7 min read

How Interpretation Conflict Vulnerability happens in Node.js and how to fix it

node-forge versions up to 1.3.1 shipped an ASN.1 parser vulnerable to an interpretation conflict that could let attackers bypass cryptographic signature verification, alongside a related unbounded recursion flaw (CVE-2025-66031) that enables denial-of-service. Upgrading the dependency to node-forge 1.4.0 patches both issues by hardening the ASN.1 decoder against malformed and adversarially crafted input.

O
By Orbis AppSec
•Technically reviewed by Anupam Mediratta•Published August 31, 2026•Reviewed August 31, 2026
#cryptography#node-forge#nodejs#asn1#dependency-vulnerability#supply-chain-security

Answer Summary

CVE-2025-12816 is an interpretation conflict vulnerability in the node-forge npm package (Node.js) that allowed attackers to craft ASN.1/DER structures which are parsed inconsistently between the verifier and the intended interpretation, enabling bypass of cryptographic signature checks (related to CWE-436). It is fixed by upgrading node-forge from 1.3.1 to 1.4.0, which also patches the related CVE-2025-66031 unbounded recursion issue in the ASN.1 parser. No application code changes were required — only the dependency version bump in package.json and package-lock.json.

Vulnerability at a Glance

cweCWE-436
fixUpgrade the `node-forge` dependency from `^1.3.1` to `^1.4.0` in package.json/package-lock.json
riskAttackers can craft malformed ASN.1/DER data that is parsed differently by node-forge than intended, potentially bypassing signature or certificate verification, or triggering unbounded recursion (DoS)
languageJavaScript (Node.js)
root causenode-forge's ASN.1 decoder (≤1.3.1) did not consistently validate structure and depth of encoded data before interpretation
vulnerabilityInterpretation Conflict in ASN.1/Cryptographic Verification (node-forge)

Introduction

The package-lock.json in this repository pinned node-forge to ^1.3.1 — a widely used pure-JavaScript implementation of TLS, ASN.1 parsing, and cryptographic primitives such as RSA, X.509 certificates, and PKCS#7/PKCS#12. Because node-forge is often used to verify certificates, decode signed payloads, or validate cryptographic material coming from untrusted sources (uploaded files, network responses, third-party SDKs), any flaw in its ASN.1 decoding logic has an outsized blast radius: it sits directly on the trust boundary between "data we received" and "data we believe is cryptographically valid."

CVE-2025-12816 describes an interpretation conflict vulnerability in node-forge that allows bypassing cryptographic verifications. In plain terms: the ASN.1/DER parser used internally by node-forge's signature and certificate verification routines could be tricked into interpreting a byte sequence differently than the verification logic expected, meaning a signature or certificate check could report "valid" for data that shouldn't pass. A closely related issue tracked in the same dependency, CVE-2025-66031 (ASN.1 Unbounded Recursion), allowed deeply nested or malformed ASN.1 structures to drive the parser into unbounded recursive calls — a classic denial-of-service vector.

Both issues live in the same subsystem — node-forge's ASN.1 decoder — and both are fixed in the same upstream release. This project's node_modules/node-forge dependency listed in package-lock.json was resolved to node-forge-1.3.1.tgz, confirmed vulnerable, and the fix simply bumps it forward.

The Vulnerability Explained

Here's the relevant diff from package-lock.json before the fix:

"node_modules/node-forge": {
  "version": "1.3.1",
  "resolved": "https://registry.npmjs.org/node-forge/-/node-forge-1.3.1.tgz",
  "integrity": "sha512-dPEtOeMvF9VMcYV/1Wb8CPoVAXtp6MKMlcbAt4ddqmGqUJ6fQZFXkNZNkNlfevtNkGtaSoXf/vNNNSvgrdXwtA==",
  ...
}

And in package.json:

"node-forge": "^1.3.1",

The ^1.3.1 semver range means npm would happily install any 1.x.x release compatible with 1.3.1, but because 1.3.1 was already the latest published version at lockfile-generation time, the lockfile pinned the exact vulnerable build. Any code in this application that calls into node-forge's ASN.1 or PKI APIs — for example forge.asn1.fromDer(), forge.pki.certificateFromPem(), or signature verification helpers built on top of them — inherits the flaw.

Why this is dangerous:

  • Interpretation conflict (CVE-2025-12816): ASN.1/DER encoding has well-defined canonical rules, but a permissive parser can accept non-canonical encodings of the same logical value (e.g., alternate length encodings, redundant padding, or ambiguous tag interpretation). If the verification logic and the parsing logic disagree on what a byte sequence "means," an attacker can construct a certificate or signed blob that decodes to a benign structure for validation purposes while a downstream consumer treats it as something else — effectively bypassing the cryptographic check.
  • Unbounded recursion (CVE-2025-66031): ASN.1 structures can be nested (SEQUENCE within SEQUENCE, etc.). Without a depth limit, a maliciously crafted, deeply nested DER blob forces the parser into recursive descent with no bound, exhausting the call stack or CPU and crashing the Node.js process.

Example attack scenario: Imagine this application uses node-forge anywhere it accepts a PEM/DER certificate or a signed payload from an external source — a plugin update package, a webhook signature, or a SaaS integration response. An attacker submits a crafted certificate blob. Because of the interpretation conflict, node-forge's verification path reports the signature as valid even though the "real" interpretation of the payload (as consumed elsewhere in the pipeline) differs from what was verified — a classic verification bypass. Alternatively, the attacker submits a deeply nested ASN.1 structure as a "certificate," and the parser recurses until the process stack overflows, taking down the service that was validating it.

The Fix

The fix here is intentionally minimal and low-risk: bump the dependency, don't touch application logic.

package.json:

-    "node-forge": "^1.3.1",
+    "node-forge": "^1.4.0",

package-lock.json:

-      "version": "1.3.1",
-      "resolved": "https://registry.npmjs.org/node-forge/-/node-forge-1.3.1.tgz",
-      "integrity": "sha512-dPEtOeMvF9VMcYV/1Wb8CPoVAXtp6MKMlcbAt4ddqmGqUJ6fQZFXkNZNkNlfevtNkGtaSoXf/vNNNSvgrdXwtA==",
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/node-forge/-/node-forge-1.4.0.tgz",
+      "integrity": "sha512-LarFH0+6VfriEhqMMcLX2F7SwSXeWwnEAJEsYm5QKWchiVYVvJyV9v7UDvUv+w5HO23ZpQTXDv/GxdDdMyOuoQ==",

Both files needed to change together: package.json declares the intended version range so future npm install runs resolve safely, while package-lock.json pins the exact resolved version and integrity hash that will actually be installed in CI/CD and production builds. Updating only one would either leave the lockfile stale (npm would keep resolving 1.3.1 on a clean install) or leave package.json's declared range inconsistent with what's actually shipped.

Node-forge 1.4.0 hardens the ASN.1 decoder by:
- Enforcing stricter, canonical interpretation of DER/BER length and tag encodings, closing the interpretation-conflict gap that allowed verification bypass (CVE-2025-12816).
- Adding recursion/depth guards when walking nested ASN.1 structures, preventing the unbounded recursion crash (CVE-2025-66031).

Because this is a dependency-only change with no altered call sites in this repository's own code, existing valid certificates, signatures, and PKI operations continue to work exactly as before — only maliciously malformed input is now rejected instead of silently accepted or causing a crash.

Key Takeaways

  • node-forge 1.3.1 and earlier are vulnerable to both an ASN.1 interpretation-conflict bypass (CVE-2025-12816) and an unbounded-recursion DoS (CVE-2025-66031) — upgrading to 1.4.0 fixes both.
  • The fix required changing exactly two files, package.json and package-lock.json, and zero application code — a reminder that dependency hygiene alone can close a high-severity crypto bypass.
  • Any code path in this project that verifies certificates, PKCS#7/PKCS#12 structures, or signatures via node-forge was implicitly exposed to this flaw and is now protected.
  • Semver ranges like ^1.3.1 don't automatically protect you — you still need active scanning to know when a "compatible" version becomes the safe one to move to.
  • Cryptographic verification bypasses rarely announce themselves; they fail silently by returning "valid" for data that shouldn't be trusted, which is why continuous SCA scanning matters more here than for typical logic bugs.

How Orbis AppSec Detected This

  • Source: Any untrusted ASN.1/DER-encoded input passed into node-forge — e.g., certificates, signed payloads, or PKI material received from external clients, uploads, or third-party integrations.
  • Sink: node-forge's internal ASN.1 decoder and signature/certificate verification routines (forge.asn1.fromDer(), forge.pki.* verification paths) bundled in node_modules/node-forge as declared in package-lock.json.
  • Missing control: The installed node-forge@1.3.1 lacked strict canonical ASN.1 interpretation and recursion-depth limits, allowing malformed input to either bypass verification or exhaust resources.
  • CWE: CWE-436 (Interpretation Conflict), related to CWE-674 (Uncontrolled Recursion) / CWE-400 (Uncontrolled Resource Consumption) for the DoS variant.
  • Fix: Upgraded the node-forge dependency from ^1.3.1 to ^1.4.0 in package.json and package-lock.json, pulling in the patched ASN.1 decoder.

Orbis AppSec automatically detected this vulnerability and opened a pull request with the fix. Try Orbis AppSec on your repositories to find and fix issues like this automatically.

Conclusion

This case is a clean example of why dependency management is a first-class security control, not an afterthought. A single outdated version of node-forge sitting in package-lock.json meant that any cryptographic verification performed by this application inherited an interpretation-conflict bug capable of bypassing signature checks, plus a recursion bug capable of crashing the process. The fix was a two-line version bump — but only because automated scanning flagged the exact vulnerable dependency and version. Keep your cryptographic libraries current, automate the scanning that catches issues like CVE-2025-12816, and treat every "just a dependency bump" PR involving a crypto library with the seriousness it deserves.

Prevention and further reading

View the Security Fix

Check out the pull request that fixed this vulnerability

View PR #4
View Repository →

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