Affects widely used NGINX data plane (njs/QuickJS) and SAML reference implementation; can cause outages across web infrastructure and is high-severity (CVSS 9.2).
CVE-2026-78689
NGINX njs/QuickJS XML parser OOB write via xml.exclusiveC14n causing DoS and possible RCE
Is CVE-2026-78689 being exploited?
Not confirmed. CVE-2026-78689 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 0.45% probability of exploitation in the next 30 days.
How severe is CVE-2026-78689?
CVE-2026-78689 is rated Critical with a CVSS score of 9.2. 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-2026-78689?
Not known from our data. No patch reference has been recorded for CVE-2026-78689, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-78689 affect?
CVE-2026-78689 affects NGINX (njs JavaScript engine), NGINX (QuickJS engine), nginxinc/nginx-saml reference implementation. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-78689?
Block/validate untrusted XML/SAML PrefixList; avoid xml.exclusiveC14n on untrusted input; apply vendor patch when released.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated remote attacker can crash workers (DoS), cause memory growth/leak, and may enable code execution via crafted XML namespace PrefixList.
Immediate action required
- affected>= 0.7.10 and < 1.0.1
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.