CVE-2023-42450Network attack vector

SSRF via faulty URL path normalization

Published Sep 19, 2023 · Updated Jun 18, 2025

SSRF in Mastodon 4.2.0-beta1 through 4.2.0-rc1 allows remote attackers to inject data into outbound HTTP requests. Request in app/lib/request.rb applies a custom URL normalizer that insufficiently validates and escapes path components, permitting CRLF header injection and HTTP request splitting. Impact requires ALLOWED_PRIVATE_ADDRESSES to expose an exploitable local service and is limited to resources reachable through that confused-deputy path.

CVSS severity7.5
High
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Mastodon 4.2.0-beta1 through 4.2.0-rc1 allows remote attackers to inject data into outbound HTTP requests. Request in app/lib/request.rb applies a custom URL normalizer that insufficiently validates and escapes path components, permitting CRLF header injection and HTTP request splitting. Impact requires ALLOWED_PRIVATE_ADDRESSES to expose an exploitable local service and is limited to resources reachable through that confused-deputy path.

The record

CVE
CVE-2023-42450
Published
Sep 19, 2023
Updated
Jun 18, 2025
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-918, CWE-113, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 19, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 18, 2025Record 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=>= 4.2.0-beta1, < 4.2.0-rc2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=>= 4.2.0-beta1, < 4.2.0-rc2

Published CVSS scores

5.4GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
T1190Exploit Public-Facing Application

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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