CVE-2026-82450

HIGHPre-NVD 8.88.8—
EchelonGraph scoreHIGH confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-08-29. a secondary CVSS source baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.8
EG Score
8.8(high)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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 computed
Severity88% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
46%
KEV
Not listed

Published

August 29, 2026

Last Modified

August 31, 2026

Advisory Details (3)

Auto-updated Aug 29, 2026
Patch 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-cover
generic

GitHub - BookStackApp/BookStack: NOW MANAGED ON CODEBERG · GitHub

https://github.com/BookStackApp/BookStack
github_commit Patch Available

commit e210cc32e4cb (BookStackApp/BookStack)

Patch available: BookStackApp/BookStack v26.05.4 (contains commit e210cc32e4cb)

https://github.com/BookStackApp/BookStack/commit/e210cc32e4cbb1efeae5c5c9d0fef8e3c6a752e6

Vendor 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 25× in last 7d / 88× 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.

  1. 2026-09-21 15:49 UTCGHSA enrichment
  2. 2026-09-21 02:49 UTCEG score recompute
  3. 2026-09-21 02:49 UTCGHSA enrichment
  4. 2026-09-20 20:16 UTCEPSS rescore
  5. 2026-09-20 13:49 UTCGHSA enrichment
  6. 2026-09-20 00:50 UTCEG score recompute
  7. 2026-09-20 00:49 UTCGHSA enrichment
  8. 2026-09-19 11:48 UTCGHSA enrichment
  9. 2026-09-18 22:48 UTCEG score recompute
  10. 2026-09-18 22:48 UTCGHSA enrichment
  11. 2026-09-18 19:28 UTCEPSS rescore
  12. 2026-09-18 09:49 UTCGHSA enrichment
  13. 2026-09-17 20:50 UTCEG score recompute
  14. 2026-09-17 20:50 UTCGHSA enrichment
  15. 2026-09-17 03:43 UTCGHSA enrichment
  16. 2026-09-16 14:44 UTCEG score recompute
  17. 2026-09-16 14:44 UTCGHSA enrichment
  18. 2026-09-16 14:08 UTCEPSS rescore
  19. 2026-09-16 05:15 UTCEPSS rescore
  20. 2026-09-16 01:44 UTCGHSA enrichment
  21. 2026-09-15 12:44 UTCEG score recompute
  22. 2026-09-15 12:44 UTCGHSA enrichment
  23. 2026-09-15 03:12 UTCEPSS rescore
  24. 2026-09-15 03:12 UTCEPSS rescore
  25. 2026-09-14 23:44 UTCGHSA enrichment
Show 63 more
  1. 2026-09-14 10:44 UTCGHSA enrichment
  2. 2026-09-13 21:45 UTCEG score recompute
  3. 2026-09-13 21:45 UTCGHSA enrichment
  4. 2026-09-13 08:45 UTCGHSA enrichment
  5. 2026-09-12 19:46 UTCEG score recompute
  6. 2026-09-12 19:46 UTCGHSA enrichment
  7. 2026-09-12 06:46 UTCGHSA enrichment
  8. 2026-09-11 17:45 UTCEG score recompute
  9. 2026-09-11 17:45 UTCGHSA enrichment
  10. 2026-09-11 14:53 UTCEPSS rescore
  11. 2026-09-11 14:53 UTCEPSS rescore
  12. 2026-09-11 04:45 UTCGHSA enrichment
  13. 2026-09-10 15:46 UTCEG score recompute
  14. 2026-09-10 15:46 UTCGHSA enrichment
  15. 2026-09-10 02:46 UTCGHSA enrichment
  16. 2026-09-09 13:47 UTCGHSA enrichment
  17. 2026-09-09 00:25 UTCEG score recompute
  18. 2026-09-09 00:25 UTCGHSA enrichment
  19. 2026-09-08 22:01 UTCEPSS rescore
  20. 2026-09-08 11:23 UTCGHSA enrichment
  21. 2026-09-08 11:21 UTCGHSA enrichment
  22. 2026-09-07 22:21 UTCEG score recompute
  23. 2026-09-07 22:21 UTCGHSA enrichment
  24. 2026-09-07 09:21 UTCGHSA enrichment
  25. 2026-09-06 20:13 UTCEG score recompute
  26. 2026-09-06 20:13 UTCGHSA enrichment
  27. 2026-09-06 13:48 UTCEPSS rescore
  28. 2026-09-06 07:13 UTCGHSA enrichment
  29. 2026-09-05 18:13 UTCEG score recompute
  30. 2026-09-05 18:13 UTCGHSA enrichment
  31. 2026-09-05 15:31 UTCEPSS rescore
  32. 2026-09-05 05:12 UTCGHSA enrichment
  33. 2026-09-04 16:13 UTCEG score recompute
  34. 2026-09-04 16:12 UTCGHSA enrichment
  35. 2026-09-04 05:07 UTCEPSS rescore
  36. 2026-09-04 03:13 UTCGHSA enrichment
  37. 2026-09-03 14:13 UTCGHSA enrichment
  38. 2026-09-03 01:13 UTCEG score recompute
  39. 2026-09-03 01:12 UTCGHSA enrichment
  40. 2026-09-02 14:12 UTCEPSS rescore
  41. 2026-09-02 12:12 UTCGHSA enrichment
  42. 2026-09-01 23:09 UTCEG score recompute
  43. 2026-09-01 23:09 UTCGHSA enrichment
  44. 2026-09-01 13:54 UTCEPSS rescore
  45. 2026-09-01 10:09 UTCEG score recompute
  46. 2026-09-01 10:09 UTCGHSA enrichment
  47. 2026-09-01 04:40 UTCEPSS rescore
  48. 2026-09-01 04:40 UTCEPSS rescore
  49. 2026-08-31 21:09 UTCGHSA enrichment
  50. 2026-08-31 19:29 UTCEG score recompute
  51. 2026-08-31 19:29 UTCGHSA enrichment
  52. 2026-08-31 18:33 UTCEG score recompute
  53. 2026-08-31 18:33 UTCGHSA enrichment
  54. 2026-08-31 05:23 UTCEG score recompute
  55. 2026-08-31 05:23 UTCGHSA enrichment
  56. 2026-08-30 19:18 UTCEPSS rescore
  57. 2026-08-30 19:17 UTCEPSS rescore
  58. 2026-08-30 16:23 UTCGHSA enrichment
  59. 2026-08-30 03:23 UTCEG score recompute
  60. 2026-08-30 03:23 UTCGHSA enrichment
  61. 2026-08-29 14:23 UTCEG score recompute
  62. 2026-08-29 13:53 UTCEG score recompute
  63. 2026-08-29 13:52 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

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, with the most recent update on August 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-82450 actively exploited?
CVE-2026-82450 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 54.0% of all scored CVEs.
What is the CVSS score of CVE-2026-82450?
CVE-2026-82450 has a CVSS v3 base score of 8.8 (NVD).
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

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