Affects widely used NGINX web server; potential global DoS via worker crash.
CVE-2026-27651
DoS via crafted requests causing NGINX worker termination
Is CVE-2026-27651 being exploited?
Not confirmed. CVE-2026-27651 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 0.94% probability of exploitation in the next 30 days.
How severe is CVE-2026-27651?
CVE-2026-27651 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-2026-27651?
Yes. A fix has been recorded for CVE-2026-27651. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-27651 affect?
CVE-2026-27651 affects NGINX Plus, NGINX Open Source, ngx_mail_auth_http_module. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-27651?
Upgrade to patched version when available
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Denial of service: crafted CRAM-MD5/APOP requests can crash workers and disrupt service
Patch when possible
- affected>= 1.29.0 and < 1.29.7
- affected>= 0.5.15 and < 1.28.3
- affected>= R36 and < R36 P3
- affected>= R35 and < R35 P2
- affected>= R34 and < *
- affected>= R33 and < *
- affected>= R32 and < R32 P5
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.