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CVE Record

CVE-2026-33891: Forge has Denial of Service via Infinite Loop in BigInteger.modInverse() with Zero Input

Forge (also called `node-forge`) is a native implementation of Transport Layer Security in JavaScript. Prior to version 1.4.0, a Denial of Service (DoS) vulnerability exists in the node-forge library due to an infinite loop in the BigInteger.modInverse() function (inherited from the bundled jsbn library). When modInverse() is called with a zero value as input, the internal Extended Euclidean Algorithm enters an unreachable exit condition, causing the process to hang indefinitely and consume 100% CPU. 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

CVE-2026-33891 is a denial-of-service flaw in Forge, also known as node-forge. A specific zero input to a math routine can make affected applications hang and consume CPU indefinitely. The issue affects versions before 1.4.0 and is patched in 1.4.0.

Executive priority

Treat as a high-priority availability issue for internet-facing or business-critical services using Forge. It does not indicate data theft, but a vulnerable reachable path could tie up CPU and disrupt service.

Technical view

Forge before 1.4.0 contains an infinite loop in BigInteger.modInverse(), inherited from bundled jsbn. When modInverse() receives zero, the Extended Euclidean Algorithm can enter an unreachable exit condition, causing 100% CPU and process hang. The CVSS 3.1 score is 7.5, availability impact high.

Likely exposure

Exposure is likely in JavaScript or Node.js applications that directly or transitively include digitalbazaar forge versions below 1.4.0 and execute the vulnerable modInverse() path with attacker-influenced input.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. The CVSS vector indicates remote, unauthenticated, low-complexity availability impact, but practical exploitability depends on whether application logic reaches modInverse() with zero input.

Researcher notes

Key evidence is the GitHub advisory and fixing commit. The vulnerability maps to CWE-606 and CWE-835. Current evidence names digitalbazaar forge below 1.4.0 only; do not broaden scope without vendor confirmation.

Mitigation direction

  • Upgrade forge or node-forge to version 1.4.0 or later.
  • Review lockfiles and SBOMs for transitive forge versions below 1.4.0.
  • Apply relevant Red Hat advisories where packaged products are in scope.
  • Check vendor guidance if upgrade timing or distribution packaging is unclear.

Validation and detection

  • Confirm no deployed application resolves forge below version 1.4.0.
  • Identify services that call or bundle BigInteger.modInverse() from forge/jsbn.
  • Verify dependency scanners flag CVE-2026-33891 and close after upgrade.
  • Review Red Hat CSAF or errata applicability for managed platforms.
Prepared
Confidence
high
Sources
8

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-606: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-835: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-33891 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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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:N/A:H

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:N/A:H3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-33891Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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: node-forge: Denial of Service via infinite loop in BigInteger.modInverse()
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T21:01:34.410Z: Reported to Red Hat.
  • 2026-03-27T20:43:37.725Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
digitalbazaarforge< 1.4.0Listed
Weakness

CWE details

CWE-606CWE-835

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

CWE-606 · source CWE mapping

Unchecked Input for Loop Condition

Unchecked Input for Loop Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-835 · source CWE mapping

Loop with Unreachable Exit Condition ('Infinite Loop')

Loop with Unreachable Exit Condition ('Infinite Loop') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs