CVE-2026-59825Network attack vector

Man-in-the-middle tampering via global TLS verify disablement

Published Aug 18, 2026 · Updated Aug 18, 2026

Improper certificate validation in Mastodon before 4.4.19 and 4.5.0 through 4.5.11 allows attackers to intercept or alter outbound TLS traffic. In app/models/concerns/user/ldap_authenticable.rb, LDAP setup writes VERIFY_NONE into OpenSSL::SSL::SSLContext::DEFAULT_PARAMS instead of a copy, so a local LDAP setting disables certificate checks process-wide for puma web requests. Exposure requires LDAP authentication with LDAP_TLS_NO_VERIFY=true; sidekiq jobs are not affected, but man-in-the-middle attackers on the network path can spoof remote TLS endpoints reached by web processes.

CVSS severity7.4
High
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Mastodon before 4.4.19 and 4.5.0 through 4.5.11 allows attackers to intercept or alter outbound TLS traffic. In app/models/concerns/user/ldap_authenticable.rb, LDAP setup writes VERIFY_NONE into OpenSSL::SSL::SSLContext::DEFAULT_PARAMS instead of a copy, so a local LDAP setting disables certificate checks process-wide for puma web requests. Exposure requires LDAP authentication with LDAP_TLS_NO_VERIFY=true; sidekiq jobs are not affected, but man-in-the-middle attackers on the network path can spoof remote TLS endpoints reached by web processes.

The record

CVE
CVE-2026-59825
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record 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=< 4.4.19
  2. Affected versionversion=>= 4.5.0, < 4.5.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=< 4.4.19; version=>= 4.5.0, < 4.5.12

Published CVSS scores

7.4GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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