CVE-2018-21018

CRITICALNVD 9.89.8—

9.8

Mastodon before 2.6.3 mishandles timeouts of incompletely established sessions.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 83.5%
KEV: Not listed

Published

September 22, 2019

Last Modified

November 21, 2024

Advisory Details (4)

Auto-updated May 27, 2026

Patch available. Sources: github_pr, github_release.

github_release Patch Available

v2.6.3

Patch available: tootsuite/mastodon v2.6.3

https://github.com/tootsuite/mastodon/releases/tag/v2.6.3

github_release Patch Available

v2.6.2

Patch available: tootsuite/mastodon v2.6.2

https://github.com/tootsuite/mastodon/releases/tag/v2.6.2

github_pr Patch Available

Fix TLS handshake timeout not being enforced

Patch available: tootsuite/mastodon v4.5.1 (PR #9381 merged 2018-11-27)

https://github.com/tootsuite/mastodon/pull/9381

github_pr Patch Available

Fix connect timeout not being enforced

Patch available: tootsuite/mastodon v4.5.1 (PR #9329 merged 2018-11-22)

https://github.com/tootsuite/mastodon/pull/9329

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-613Insufficient Session Expiration

Data Freshness Timeline

(refreshed 8× in last 7d / 8× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-27 14:03 UTCEG score recompute
2026-05-27 14:03 UTCGHSA enrichment
2026-05-27 13:38 UTCepss_batch
2026-05-27 13:38 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2018-21018?

CVE-2018-21018 is a critical vulnerability published on September 22, 2019. Mastodon before 2.6.3 mishandles timeouts of incompletely established sessions.

When was CVE-2018-21018 disclosed?

CVE-2018-21018 was first published in the National Vulnerability Database on September 22, 2019, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2018-21018 actively exploited?

CVE-2018-21018 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2018-21018?

CVE-2018-21018 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2018-21018?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2018-21018, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2018-21018

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