Widely used web proxy/server; remote code execution risk; affects core NGINX Open Source and Plus.
CVE-2026-42055
Remote unauthenticated heap overflow in NGINX proxy/grpc modules via oversized headers.
Is CVE-2026-42055 being exploited?
Not confirmed. CVE-2026-42055 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 6.5% probability of exploitation in the next 30 days.
How severe is CVE-2026-42055?
CVE-2026-42055 is rated Critical. 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-2026-42055?
Yes. A fix has been recorded for CVE-2026-42055. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-42055 affect?
CVE-2026-42055 affects NGINX Plus, NGINX Open Source. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-42055?
Apply latest patch; restart NGINX; review header buffering settings.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote heap overflow in NGINX worker via large HTTP/2/GRPC headers; may allow code execution or crash, esp. if ASLR is disabled or bypassed.
Immediate action required
- affected>= 1.13.10 and < 1.31.2
- affected>= 1.30.2 and < 1.30.3
- affected>= 37.0 and < 37.0.2.1
- affected>= R36 and < R36 P6
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.