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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 versions before 1.4.0 can accept an altered Ed25519 signature that compliant implementations reject. An attacker may use this inconsistency to bypass application controls involving authentication, authorization, replay prevention, deduplication, or signed-object canonicalization. The vulnerability affects integrity rather than confidentiality or availability.

Executive priority

Treat as a high-priority integrity issue. Expedite remediation for externally reachable systems where Forge verifies Ed25519 signatures used in access decisions or anti-replay controls. Lower priority is reasonable only after confirming the vulnerable version is absent or its verification code is unreachable.

Technical view

Forge fails to reject Ed25519 signatures whose scalar S is at least the group order L. Consequently, both a valid signature and a non-canonical S + L variant can verify. This violates Ed25519 verification requirements and creates signature malleability. Forge 1.4.0 adds the missing validation.

Likely exposure

Exposure exists where forge or node-forge below 1.4.0 verifies attacker-influenced Ed25519 signatures. Risk is greatest when applications treat signature bytes as unique identifiers or use them for authentication, authorization, replay tracking, deduplication, or canonicalization. Merely having the dependency installed does not prove a reachable vulnerable path.

Exploitation context

The supplied record is not in KEV and provides no evidence of active exploitation of CVE-2026-33895. It notes that comparable signature-malleability flaws have been exploited in practice. The CVSS vector describes remote, unauthenticated, low-complexity exploitation, but real impact depends on a reachable Ed25519 verification flow and security decisions built around it.

Researcher notes

CWE-347 applies. The core defect is missing canonical-range enforcement for S, allowing an alternate byte representation of an otherwise valid signature. Researchers should distinguish cryptographic signature malleability from private-key compromise. Assess application semantics: impact becomes material when controls assume one unique signature encoding per signed message.

Mitigation direction

  • Upgrade forge or node-forge to version 1.4.0 or later.
  • Identify applications using forge for Ed25519 signature verification.
  • Prioritize internet-facing authentication, authorization, replay, and signed-object workflows.
  • Review vendor and distribution advisories for packaged dependency updates.
  • Apply compensating restrictions if immediate upgrading is not possible.

Validation and detection

  • Check manifests and lockfiles for forge or node-forge versions below 1.4.0.
  • Trace whether untrusted Ed25519 signatures reach forge verification functions.
  • Confirm production artifacts contain the upgraded dependency, not only updated manifests.
  • Verify controlled tests reject non-canonical Ed25519 signatures.
  • Regression-test authentication, authorization, replay, deduplication, and canonicalization controls.
Prepared
Confidence
high
Sources
5

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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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