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TI-2026-19304 Aliases CVE-2026-23962

Mastodon vulnerable to Denial of Service from a single post (client/server)

Priority MEDIUM 40CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-770.

Summary

Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00545 45th percentileScored 2026-11-07
Fix Fixed mastodon (mastodon): 4.3.18, 4.4.12, 4.5.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mastodonmastodonbefore 4.3.18; 4.4.0 to before 4.4.12; 4.5.0 to before 4.5.54.3.18, 4.4.12, 4.5.5Patch availableCNA
  • mastodon Vendormastodon Affected before 4.3.18; 4.4.0 to before 4.4.12; 4.5.0 to before 4.5.5 Fixed in 4.3.18, 4.4.12, 4.5.5 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*before 4.3.18; 4.4.0 to before 4.4.12; 4.5.0 to before 4.5.5Vulnerablemastodon
  • cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* Versions before 4.3.18; 4.4.0 to before 4.4.12; 4.5.0 to before 4.5.5 Vulnerable ·mastodon

Remediation

  • Fix · CNA mastodon (mastodon) Fixed in 4.3.18, 4.4.12, 4.5.5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-23962

References

Advisory 1

Other 3

  • TI-2022-02004 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon CVSS 3.1CRITICAL 9.8
  • TI-2025-34613 Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails CVSS 3.1HIGH 7.5
  • TI-2022-22936 Mastodon through 4.0.2 allows attackers to cause a denial of service (large Sidekiq pull… CVSS 3.1HIGH 7.5
  • TI-2023-18301 Mastodon vulnerable to arbitrary file creation through media attachments CVSS 3.1CRITICAL 10.0
  • TI-2023-13359 Mastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP database CVSS 3.1HIGH 7.7
  • TI-2024-16846 External OpenID Connect Account Takeover by E-Mail Change in mastodon CVSS 3.1HIGH 7.4
See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences