ws before 8.21.1 contains a memory exhaustion vulnerability in lib/receiver.js where the fragment guard only triggers when fragment count reaches maxFragments, allowing attackers to exhaust memory by sending incomplete fragmented WebSocket messages. Attackers can send a text frame with FIN=0 followed by continuation frames without completing the sequence, causing each fragment to be stored as a separate Buffer object with significant overhead, enabling denial of service through heap exhaustion.
CVE-2026-62389
HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.5 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: cna:vulncheck
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: —CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(low)
- EPSS
- —
- KEV
- Not listed
Published
July 15, 2026
Last Modified
July 15, 2026
Advisory Details (4)
Auto-updated Jul 15, 2026Patch available. Sources: github_commit, github_release.
generic
ws < 8.21.1 Default maxFragments Allows Memory Exhaustion DoS | Advisories | VulnCheck
https://www.vulncheck.com/advisories/ws-default-maxfragments-allows-memory-exhaustion-dosgithub_release Patch Available
Release 8.21.1 (websockets/ws)
Patch available: websockets/ws 8.21.1
https://github.com/websockets/ws/releases/tag/8.21.1generic
Default maxFragments still allows memory-exhaustion DoS (incomplete GHSA-96hv-2xvq-fx4p fix) · Issue #2331 · websockets/ws · GitHub
https://github.com/websockets/ws/issues/2331github_commit Patch Available
commit f197ac651409 (websockets/ws)
Patch available: websockets/ws 8.21.1 (contains commit f197ac651409)
https://github.com/websockets/ws/commit/f197ac65140920bdcecdab74bfc69c2d7858e55dVendor Advisories for CVE-2026-62389(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 2× in last 7d / 2× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-15 17:29 UTCEG score recompute
- 2026-07-15 17:28 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(4)
What is CVE-2026-62389?
CVE-2026-62389 is a high vulnerability published on July 15, 2026. ws before 8.21.1 contains a memory exhaustion vulnerability in lib/receiver.js where the fragment guard only triggers when fragment count reaches maxFragments, allowing attackers to exhaust memory by sending incomplete fragmented WebSocket messages. Attackers can send a text frame with FIN=0…
When was CVE-2026-62389 disclosed?
CVE-2026-62389 was first published in the National Vulnerability Database on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-62389?
CVE-2026-62389 has a CVSS v3 base score of 7.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-62389?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-62389, 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
Explore the affected products and dependency analysis for CVE-2026-62389
Is Your Infrastructure Affected by CVE-2026-62389?
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