CVE-2026-86430
DoS in league/commonmark <2.9.1 via crafted Markdown causing CPU exhaustion
Is CVE-2026-86430 being exploited?
Not confirmed. CVE-2026-86430 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 0.29% probability of exploitation in the next 30 days.
How severe is CVE-2026-86430?
CVE-2026-86430 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-2026-86430?
Yes. A fix has been recorded for CVE-2026-86430. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-86430 affect?
CVE-2026-86430 affects league/commonmark < 2.9.1, PHP applications using league/commonmark for Markdown parsing. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-86430?
Upgrade to league/commonmark 2.9.1+; validate and rate-limit Markdown input
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote denial of service: crafted Markdown triggers super-linear parsing CPU, exhausting server resources and blocking legitimate requests.
Patch when possible
- affected>= 0.6.0 and < 2.9.1
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.