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CVE-2016-10555: Since "algorithm" isn't enforced in jwt.decode()in jwt-simple 0.3.0 and earlier, a malicious user could cho...

Since "algorithm" isn't enforced in jwt.decode()in jwt-simple 0.3.0 and earlier, a malicious user could choose what algorithm is sent sent to the server. If the server is expecting RSA but is sent HMAC-SHA with RSA's public key, the server will think the public key is actually an HMAC private key. This could be used to forge any data an attacker wants.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

jwt-simple 0.3.0 and earlier may let an attacker trick an application into trusting forged JWT data. If the affected library protects login sessions or API authorization, the impact can be account or privilege abuse. The source bundle does not show known active exploitation.

Executive priority

Prioritize remediation for internet-facing or customer-facing authentication services first. This issue can undermine token trust, but urgency should be based on confirmed use of jwt-simple <=0.3.0 and whether JWTs control access to sensitive systems.

Technical view

The weakness is JWT algorithm confusion in jwt.decode(): the expected algorithm is not enforced. An application expecting RSA could accept HMAC-SHA using the RSA public key as an HMAC secret, allowing forged token claims. The CVE maps this to CWE-20 input validation.

Likely exposure

Exposure is likely in Node.js applications using the jwt-simple module version 0.3.0 or earlier to validate JWTs, especially where RSA-based verification is expected. Systems not using jwt-simple or not relying on JWT claims for trust decisions are not indicated as affected.

Exploitation context

The public description explains a token-forgery condition, but the bundle does not cite KEV listing, observed exploitation, exploit availability, or affected deployments. Risk depends on whether the vulnerable decode path protects authentication, authorization, or trusted user-controlled claims.

Researcher notes

Evidence supports an algorithm-confusion flaw in jwt-simple <=0.3.0 with possible JWT claim forgery. The bundle names affected product and versions, but provides no CVSS score, no KEV status, and no confirmed exploitation evidence.

Mitigation direction

  • Inventory Node.js dependencies for jwt-simple 0.3.0 or earlier.
  • Upgrade jwt-simple beyond the affected versions following vendor guidance.
  • Ensure JWT verification enforces the expected algorithm explicitly.
  • Rotate impacted keys or sessions if forged-token use is suspected.
  • Review applications that trust JWT claims for authorization decisions.

Validation and detection

  • Check package manifests and lockfiles for jwt-simple versions.
  • Identify code paths calling jwt.decode() for authentication or authorization.
  • Confirm mismatched JWT algorithms are rejected in security tests.
  • Verify RSA-verification paths do not treat public keys as HMAC secrets.
  • Review auth logs for unusual token-claim or privilege patterns.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2016-10555 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
HackerOnejwt-simple node module<=0.3.0Listed
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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