CVE-2026-65623
WebSocket fragmentation bug allows CPU-exhausting remote DoS in Bandit.
Is CVE-2026-65623 being exploited?
Not confirmed. CVE-2026-65623 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.39% probability of exploitation in the next 30 days.
How severe is CVE-2026-65623?
CVE-2026-65623 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-65623?
Yes. A fix has been recorded for CVE-2026-65623. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-65623 affect?
CVE-2026-65623 affects bandit 1.11.0 - <1.12.1, Elixir applications using Bandit WebSocket. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-65623?
Upgrade Bandit to >=1.12.1; if delayed, apply WAF/rate limits on fragmented frames.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated attacker can send many tiny WebSocket continuation frames to trigger quadratic reassembly, exhausting CPU and causing remote DoS.
Immediate action required
- affected>= 1.11.0 and < 1.12.1
- affected>= 21612c7c7b1ce43eccd36d3af3a2299d23513667 and < 418ef7e906192a230ddba112f7a669c87b6b0e3a
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.