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CVE Record

CVE-2026-1528: undici is vulnerable to Malicious WebSocket 64-bit length overflows undici parser and crashes the client

ImpactA server can reply with a WebSocket frame using the 64-bit length form and an extremely large length. undici's ByteParser overflows internal math, ends up in an invalid state, and throws a fatal TypeError that terminates the process. Patches Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-1528 is a denial-of-service issue in undici, a JavaScript HTTP client. A malicious WebSocket server can send a frame with an extremely large 64-bit length value, causing the client process to crash. The impact is service availability, not data theft or code execution based on the supplied sources.

Executive priority

Prioritize patching internet-facing or business-critical services that use undici WebSocket clients. This is a high availability risk because exploitation can crash processes, but the supplied evidence does not indicate confidentiality impact, integrity impact, or confirmed active exploitation.

Technical view

Affected undici versions are 6.0.0 before 6.24.0 and 7.0.0 before 7.24.0. The ByteParser mishandles oversized WebSocket 64-bit frame lengths, overflows internal math, enters an invalid state, and throws a fatal TypeError. CVSS is 7.5, network exploitable, low complexity, unauthenticated, availability-only.

Likely exposure

Exposure is most likely in Node.js applications that use undici directly or transitively as a WebSocket client, especially when connecting to untrusted, attacker-controlled, or compromised WebSocket servers. Downstream Red Hat packages may need product-specific review.

Exploitation context

The supplied bundle does not show CISA KEV listing or confirmed active exploitation. The documented attack condition is a malicious server response to a vulnerable WebSocket client. This can terminate the client process, so risk depends on restart behavior and business reliance on affected services.

Researcher notes

Focus validation on dependency resolution and runtime packaging, not only package.json declarations. The key condition is client-side parsing of a malicious WebSocket frame length. Evidence supports denial of service through fatal process termination; no supplied source supports remote code execution.

Mitigation direction

  • Upgrade undici to 6.24.0, 7.24.0, or later.
  • Refresh lockfiles and rebuild affected application images.
  • Review Red Hat advisories for downstream package status.
  • Avoid untrusted WebSocket endpoints until vulnerable clients are patched.
  • Monitor for process crashes tied to WebSocket activity.

Validation and detection

  • Inventory direct and transitive undici versions in SBOMs and lockfiles.
  • Confirm runtime images contain undici 6.24.0, 7.24.0, or later.
  • Run dependency scanning for CVE-2026-1528 across repositories.
  • Review logs for fatal TypeError crashes during WebSocket use.
  • Regression-test WebSocket client workflows after upgrading.
Prepared
Confidence
high
Sources
10

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-1284: 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.

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cwe · low confidence lookup

CWE-248: 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.

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cve · low confidence lookup

CVE-2026-1528 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
22Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: 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:H3.93.6openjs
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-2026-1528Attack 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-SADPundici: undici: Denial of Service via crafted WebSocket frame with large length
other:Red Hat severity ratingcvssV3_1
  • 2026-03-12T21:01:36.954Z: Reported to Red Hat.
  • 2026-03-12T20:21:57.775Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
undiciundiciundici, >= 6.0.0 < 6.24.0; 7.0.0 < 7.24.0, 6.24.0: 7.24.0unaffected
Weakness

CWE details

CWE-1284CWE-248

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

CWE-1284 · source CWE mapping

Improper Validation of Specified Quantity in Input

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

Open CWE intelligenceSame-CWE CVEs
CWE-248 · source CWE mapping

Uncaught Exception

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

Open CWE intelligenceSame-CWE CVEs