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CVE Record

CVE-2021-23384: Open Redirect

The package koa-remove-trailing-slashes before 2.0.2 are vulnerable to Open Redirect via the use of trailing double slashes in the URL when accessing the vulnerable endpoint (such as https://example.com//attacker.example/). The vulnerable code is in index.js::removeTrailingSlashes(), as the web server uses relative URLs instead of absolute URLs.

MediumCVSS 5.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Applications using vulnerable koa-remove-trailing-slashes can redirect users to an unintended external site when malformed paths are normalized. This is mainly a phishing and trust-abuse risk, not a server takeover. The affected package is fixed in versions 2.0.2 and later according to the source bundle.

Executive priority

Treat as a moderate-priority web trust issue. It is unlikely to cause direct system compromise, but public customer-facing applications should remediate promptly because open redirects can support phishing and damage user confidence.

Technical view

The flaw is in removeTrailingSlashes(), where relative redirect targets are used while stripping trailing slashes. A URL with double slashes can be interpreted as a scheme-relative destination, producing an open redirect. Affected scope is koa-remove-trailing-slashes before 2.0.2.

Likely exposure

Exposure is limited to Node/Koa applications that directly or transitively use koa-remove-trailing-slashes before 2.0.2 on public routes. Risk is higher where redirects affect login, onboarding, password reset, or customer-facing links.

Exploitation context

The bundle does not show KEV listing or confirmed active exploitation. Exploitation requires user interaction: a victim must follow a crafted link to a vulnerable endpoint. Potential impact is credential phishing, brand abuse, and limited confidentiality or integrity loss through misdirection.

Researcher notes

The public record attributes the issue to index.js removeTrailingSlashes() using relative URLs. The source bundle provides affected package and fixed-version information, but no confirmed exploitation evidence, no CWE mapping, and no broader affected-product list.

Mitigation direction

  • Upgrade koa-remove-trailing-slashes to version 2.0.2 or later.
  • Review dependency locks for transitive use of the package.
  • Prefer absolute, same-origin redirect targets in redirect middleware.
  • Check vendor guidance if package constraints block upgrading.

Validation and detection

  • Inventory applications using koa-remove-trailing-slashes.
  • Confirm installed versions are 2.0.2 or later.
  • Review public Koa routes that normalize trailing slashes.
  • Test redirect handling in a safe staging environment.
  • Verify security scanners no longer flag CVE-2021-23384.
Prepared
Confidence
high
Sources
4

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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CVE-2021-23384 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
Medium
CVSS
5.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C

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.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

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
5.4CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C2.82.5Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.4Medium
CVSS 3.1 vector shape for CVE-2021-23384Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C

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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/akoa-remove-trailing-slashesunspecifiedListed
Weakness

CWE details

No CWE listed

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