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CVE Record

CVE-2026-4926: path-to-regexp vulnerable to Denial of Service via sequential optional groups

Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service. Patches: Fixed in version 8.4.0. Workarounds: Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-4926 is a denial-of-service issue in path-to-regexp. Certain route patterns with repeated optional groups can produce a regular expression that grows exponentially, potentially consuming availability. It affects business services only where vulnerable versions and risky route patterns are present.

Executive priority

Prioritize remediation for internet-facing or high-availability services that use path-to-regexp. The issue is availability-focused, not data theft, but unauthenticated network-triggered denial of service can still create operational impact.

Technical view

path-to-regexp can generate pathological regular expressions from multiple sequential optional groups using curly brace syntax. The CVSS 3.1 score is 7.5, driven by network reachability, low attack complexity, no privileges, no user interaction, and high availability impact.

Likely exposure

Exposure is most likely in Node.js applications or downstream products using path-to-regexp 8.x before the stated 8.4.0 fix, especially where route patterns contain sequential optional groups or are built from user-controlled input.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. The practical risk is availability loss when vulnerable pattern generation is reachable in application routing or dynamic route configuration paths.

Researcher notes

Relevant weaknesses are CWE-1333 and CWE-400. Validate exposure through dependency and route-pattern review, not exploit reproduction. The provided sources identify the cause and fixed version, but downstream product impact depends on each vendor advisory.

Mitigation direction

  • Upgrade path-to-regexp to version 8.4.0 or later where applicable.
  • Limit sequential optional groups in route patterns.
  • Do not pass user-controlled input as route patterns.
  • Review Red Hat advisories for downstream package status.
  • Check vendor guidance for product-specific remediation details.

Validation and detection

  • Inventory direct and transitive path-to-regexp usage.
  • Confirm deployed versions against the 8.4.0 fixed release.
  • Review route definitions for sequential optional curly-brace groups.
  • Verify no user-controlled data can define route patterns.
  • Track Red Hat CSAF or errata applicability for managed platforms.
Prepared
Confidence
medium
Sources
12

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-1333: 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-400: 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-2026-4926 mapping review

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

Open ATT&CK lookup
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
21Source 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-2026-4926Attack 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-SADPpath-to-regexp: path-to-regexp: Denial of Service via crafted regular expressions
other:Red Hat severity ratingcvssV3_1
  • 2026-03-26T20:03:28.427Z: Reported to Red Hat.
  • 2026-03-26T18:59:38.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
path-to-regexppath-to-regexp8.0.0, 8.4.0unaffected
Weakness

CWE details

CWE-1333CWE-400

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

CWE-1333 · source CWE mapping

Inefficient Regular Expression Complexity

Inefficient Regular Expression Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

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

Open CWE intelligenceSame-CWE CVEs