What’s Vulnerable › Vulnerabilities

CVE-2026-59825: Mastodon: Unwanted deactivation of SSL/TLS certificate verification

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-18 · updated 2026-09-16
• Weakness: CWE-295

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.19 and from 4.5.0 until 4.5.12, Mastodon's app/models/concerns/user/ldap_authenticable.rb mutates OpenSSL::SSL::SSLContext::DEFAULT_PARAMS when LDAP authentication uses LDAP_TLS_NO_VERIFY=true, disabling SSL and TLS certificate verification globally for requests made by puma web processes while sidekiq background jobs remain unaffected. This issue is fixed in versions 4.4.19 and 4.5.12.

Affected products

• mastodon: before 4.4.19; from 4.5.0, < 4.5.12

References

• https://github.com/mastodon/mastodon/commit/2ccb6ef277e725d1932295690cf8ab9d3dc03149
• https://github.com/mastodon/mastodon/commit/5748d0b16ea09001e0933f76c7afe814e09652ef
• https://github.com/mastodon/mastodon/commit/761c61b42590a2fd91442fc15a0a7583e48bbea4
• https://github.com/mastodon/mastodon/pull/39571
• https://github.com/mastodon/mastodon/releases/tag/v4.4.19
• https://github.com/mastodon/mastodon/releases/tag/v4.5.12
• https://github.com/mastodon/mastodon/security/advisories/GHSA-3rhr-8phh-jm86

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