CVE-2026-82450
RCE via crafted ZIP book cover in BookStack (<26.05.4).
Is CVE-2026-82450 being exploited?
Not confirmed. CVE-2026-82450 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 0.57% probability of exploitation in the next 30 days.
How severe is CVE-2026-82450?
CVE-2026-82450 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-2026-82450?
Yes. A fix has been recorded for CVE-2026-82450. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-82450 affect?
CVE-2026-82450 affects BookStack < 26.05.4, BookStack Portable ZIP import feature, Self-hosted BookStack instances. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-82450?
Upgrade to 26.05.4 or apply patch; restrict Import/Create Books perms and block .php uploads.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution: attacker uploads PHP polyglot in ZIP import, stored in web root and executed via unauthenticated HTTP requests.
Immediate action required
- affected< 26.05.4
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.