CVE-2021-32643Network attack vector

Directory-existence disclosure via scheme-blind path check

Published May 27, 2021 · Updated Aug 3, 2024

Information disclosure in affected http4s versions allows remote attackers to infer server directory existence through HTTP responses. StaticFile.fromUrl constructs a local File from URL.getFile and tests isDirectory before verifying that the URL uses the file scheme or opening its connection. Exposure requires application code to pass a fetchable non-file URL whose path matches a server directory; the resulting 404 oracle reveals only directory existence, not contents or metadata.

CVSS severity5.8
Medium
EPSS probability1.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in affected http4s versions allows remote attackers to infer server directory existence through HTTP responses. StaticFile.fromUrl constructs a local File from URL.getFile and tests isDirectory before verifying that the URL uses the file scheme or opening its connection. Exposure requires application code to pass a fetchable non-file URL whose path matches a server directory; the resulting 404 oracle reveals only directory existence, not contents or metadata.

The record

CVE
CVE-2021-32643
Published
May 27, 2021
Updated
Aug 3, 2024
Vendor
http4s
Product
http4s
Classifications
CWE-22, T1083
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.21.7, < 0.21.24
  2. Affected versionversion=>= 0.22.0-M1, <= 0.22.0-M8
  3. Affected versionversion== 0.23.0-M1
  4. Affected versionversion=>= 1.0.0-M1, < 1.0.0-M23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

http4s · http4sversion=>= 0.21.7, < 0.21.24; version=>= 0.22.0-M1, <= 0.22.0-M8; version== 0.23.0-M1; version=>= 1.0.0-M1, < 1.0.0-M23

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
5.8GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1083File and Directory Discovery

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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