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CVE Record

CVE-2026-33895: Forge has signature forgery in Ed25519 due to missing S > L check

Forge (also called `node-forge`) is a native implementation of Transport Layer Security in JavaScript. Prior to version 1.4.0, Ed25519 signature verification accepts forged non-canonical signatures where the scalar S is not reduced modulo the group order (`S >= L`). A valid signature and its `S + L` variant both verify in forge, while Node.js `crypto.verify` (OpenSSL-backed) rejects the `S + L` variant, as defined by the specification. This class of signature malleability has been exploited in practice to bypass authentication and authorization logic (see CVE-2026-25793, CVE-2022-35961). Applications relying on signature uniqueness (i.e., dedup by signature bytes, replay tracking, signed-object canonicalization checks) may be bypassed. Version 1.4.0 patches the issue.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Forge before 1.4.0 can accept certain malformed Ed25519 signatures as valid. This can let an attacker change the signature bytes while preserving verification, undermining systems that use signatures for authorization, replay prevention, deduplication, or signed-object checks.

Executive priority

Prioritize remediation for internet-facing or identity-sensitive systems using forge Ed25519 verification. The issue has high integrity impact, no user interaction requirement, and a clear patched version.

Technical view

The Ed25519 verifier in digitalbazaar forge/node-forge does not reject non-canonical S values where S is at least the group order L. The advisory states both a valid signature and its S+L variant verify in forge, contrary to RFC8032 expectations and OpenSSL-backed Node.js behavior.

Likely exposure

Exposure is likely where applications depend on forge/node-forge versions below 1.4.0 and use its Ed25519 signature verification. Highest concern is authentication, authorization, replay tracking, signature uniqueness, deduplication, or signed-object canonicalization logic.

Exploitation context

The bundle does not cite active exploitation of CVE-2026-33895, and KEV is false. It does note this signature-malleability class has been exploited in practice in other CVEs, so affected trust-boundary uses should be treated seriously.

Researcher notes

Focus triage on Ed25519 verification paths in forge below 1.4.0. Evidence supports non-canonical signature acceptance; it does not support claims of active exploitation for this specific CVE.

Mitigation direction

  • Upgrade forge/node-forge to version 1.4.0 or later.
  • Inventory direct and transitive dependencies for forge versions below 1.4.0.
  • Check Red Hat advisories for packaged product status and updates.
  • Review logic that relies on raw signature-byte uniqueness.
  • Follow vendor guidance if immediate upgrade is blocked.

Validation and detection

  • Confirm installed forge/node-forge versions in manifests, lockfiles, and built artifacts.
  • Identify code paths using forge for Ed25519 signature verification.
  • Verify production images and deployments contain forge 1.4.0 or later.
  • Check replay, deduplication, and signed-object checks for signature-byte assumptions.
  • Track vendor advisories and VEX status for affected packaged components.
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-347: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-33895 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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.

2CVSS vectors
5Timeline events
2ADP providers
11Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-33895Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnode-forge: Forge: Authentication bypass via forged Ed25519 cryptographic signatures
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T21:02:18.484Z: Reported to Red Hat.
  • 2026-03-27T20:47:54.492Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
digitalbazaarforge< 1.4.0Listed
Weakness

CWE details

CWE-347

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

CWE-347 · source CWE mapping

Improper Verification of Cryptographic Signature

Improper Verification of Cryptographic Signature represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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