CVE-2026-23962
Published: 22 January 2026
Summary
CVE-2026-23962 is a high-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Joinmastodon Mastodon. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 6.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
This control implements explicit throttling on session allocation, addressing the weakness of allocating resources without limits.
Plan testing exercises resource allocation limits and throttling during simulated failures, directly addressing weaknesses that allow unbounded resource use.
Contingency plan updates ensure recovery strategies address unbounded resource allocation, making it harder for attackers to exploit lack of throttling to cause prolonged outages.
Provides continuity when unbounded resource allocation at the primary site leads to exhaustion and downtime.
Alternate services allow operations to continue when primary allocation of resources lacks limits or throttling.
Explicit planning of security-related actions requires defining limits, windows, and resource allocations, making allocation without throttling far less likely.
Measures of performance include tracking allocation behavior and throttling effectiveness, reducing the window for resource exhaustion attacks.
Imposes an inactivity-based limit on network resource allocation, throttling the number of concurrently held connections.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct exploitation of public-facing Mastodon server via remote ActivityPub content to trigger application resource exhaustion DoS.
NVD Description
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…
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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.
Deeper analysisAI
CVE-2026-23962 is a resource exhaustion vulnerability in Mastodon, a free, open-source social network server based on ActivityPub. Affected versions are those prior to v4.3.18, v4.4.12, and v4.5.5, where there is no limit on the maximum number of poll options in remote posts. This allows attackers to create polls with an excessively large number of options, leading to greatly increased resource consumption and potential denial-of-service (DoS) conditions. The vulnerability is rated with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is associated with CWE-770 (Allocation of Resources Without Limits or Throttling).
Any unauthenticated attacker with network access can exploit this vulnerability by posting remote content containing a poll with a very large number of options. The disproportionate resource usage impacts both Mastodon servers and clients, depending on the scale of options included, resulting in server-side or client-side DoS.
Mitigation is available through patches released in Mastodon versions v4.3.18, v4.4.12, and v4.5.5, as detailed in the corresponding GitHub release notes and the security advisory GHSA-gg8q-rcg7-p79g. Administrators should upgrade to one of these fixed versions to prevent exploitation.
Details
- CWE(s)