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Permalink CVE-2026-25540
6.5 MEDIUM
  • CVSS version: 3.1
  • Attack vector (AV): NETWORK
  • Attack complexity (AC): LOW
  • Privileges required (PR): NONE
  • User interaction (UI): NONE
  • Scope (S): UNCHANGED
  • Confidentiality impact (C): LOW
  • Integrity impact (I): NONE
  • Availability impact (A): LOW
created 2 months, 2 weeks ago
Mastodon's signature-dependent ActivityPub collection responses cached under signature-independent keys (Web Cache Poisoning via `Rails.cache`)

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.3.19, 4.4.13, 4.5.6, Mastodon is vulnerable to web cache poisoning via `Rails.cache. When AUTHORIZED_FETCH is enabled, the ActivityPub endpoints for pinned posts and featured hashtags have contents that depend on the account that signed the HTTP request. However, these contents are stored in an internal cache and reused with no regards to the signing actor. As a result, an empty response generated for a blocked user account may be served to requests from legitimate non-blocked actors, or conversely, content intended for non-blocked actors may be returned to blocked actors. This issue has been patched in versions 4.3.19, 4.4.13, 4.5.6.

Affected products

mastodon
  • ==< 4.5.6
  • ==< 4.4.13
  • ==< 4.3.19

Matching in nixpkgs

pkgs.mastodon

Self-hosted, globally interconnected microblogging software based on ActivityPub

  • nixos-unstable -
  • nixos-25.11 4.5.3

pkgs.mastodon-bot

Bot to publish twitter, tumblr or rss posts to an mastodon account.

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