BookStack before 26.05.4 contains a remote code execution vulnerability in the portable ZIP import functionality that allows users with Import Content and Create Books permissions to upload a PHP polyglot file as a book cover. Attackers can bypass image extension validation by embedding a PHP file with a .php filename in the ZIP archive, which is stored in the public web root and executed by unauthenticated requests.
CVE-2026-82450
HIGHPre-NVD 8.88.8
EchelonGraph scoreLOW confidence
This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 8.8Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.8
- EG Score
- 8.8(low)
- EG Risk
- 44(Track)EG Risk 44/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity88% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
August 29, 2026
Last Modified
August 29, 2026
Advisory Details (3)
Auto-updated Aug 29, 2026Patch available. Sources: github_commit.
generic
BookStack before 26.05.4 Remote Code Execution via Book Cover | Advisories | VulnCheck
https://www.vulncheck.com/advisories/bookstack-before-26.05.4-remote-code-execution-via-book-covergeneric
GitHub - BookStackApp/BookStack: NOW MANAGED ON CODEBERG · GitHub
https://github.com/BookStackApp/BookStackgithub_commit Patch Available
commit e210cc32e4cb (BookStackApp/BookStack)
Patch available: BookStackApp/BookStack v26.05.4 (contains commit e210cc32e4cb)
https://github.com/BookStackApp/BookStack/commit/e210cc32e4cbb1efeae5c5c9d0fef8e3c6a752e6Vendor Advisories for CVE-2026-82450(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 3× in last 7d / 3× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-29 14:23 UTCEG score recompute
- 2026-08-29 13:53 UTCEG score recompute
- 2026-08-29 13:52 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-434
Frequently asked(4)
What is CVE-2026-82450?
CVE-2026-82450 is a high vulnerability published on August 29, 2026. BookStack before 26.05.4 contains a remote code execution vulnerability in the portable ZIP import functionality that allows users with Import Content and Create Books permissions to upload a PHP polyglot file as a book cover. Attackers can bypass image extension validation by embedding a PHP file…
When was CVE-2026-82450 disclosed?
CVE-2026-82450 was first published in the National Vulnerability Database on August 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-82450?
CVE-2026-82450 has a CVSS v3 base score of 8.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-82450?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-82450, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-82450
Is Your Infrastructure Affected by CVE-2026-82450?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.