# CVE-2026-126811: BookStack before 26.09.3 Incorrect Authorization via Image and Drawio Endpoints Status: published. Published: 2026-11-11. Updated: 2026-11-12. BookStack before 26.09.3 contains an incorrect authorization vulnerability that allows authenticated users to access other users' unpublished draft page images by checking only PageView permission without draft status. Attackers can read drawio data via the base64 endpoint or rename, replace, or delete draft images by sequential ID to disclose or tamper with unpublished work. ## Remediation - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://codeberg.org/bookstack/bookstack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://codeberg.org/bookstack/bookstack/commit/4fec06236cbfb314fd72c1b3614c7c50162fb41c - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/BookStackApp/BookStack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 ## Affected products and versions - BookStackApp / BookStack (BookStackApp/BookStack): ≥ 0; < 26.09.3 (affected, custom). Source: CNA: VulnCheck ## Severity and prioritization - CVSS 4.0: 5.3 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck - CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N; source: CNA: VulnCheck - CVSS 4.0: 5.3 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com - CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N; source: NVD: disclosure@vulncheck.com - CISA KEV: No listing in collected sources - EPSS: 0.29% as of 2026-11-12; percentile 21.73% - SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP - Weaknesses: CWE-863 ## Exploit evidence No exploit evidence in collected sources. This is not proof of no exploitation. ## References - https://codeberg.org/bookstack/bookstack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 (CNA: VulnCheck; patch) - https://codeberg.org/bookstack/bookstack/commit/4fec06236cbfb314fd72c1b3614c7c50162fb41c (CNA: VulnCheck; patch) - https://github.com/BookStackApp/BookStack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 (CNA: VulnCheck; patch) - https://www.bookstackapp.com/blog/bookstack-release-v26-09-3/ (CNA: VulnCheck; release-notes) - https://codeberg.org/bookstack/bookstack/releases/tag/v26.09.3 (CNA: VulnCheck; release-notes) - https://github.com/BookStackApp/BookStack/releases/tag/v26.09.3 (CNA: VulnCheck; release-notes) - https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/DrawioImageController.php#L82-L92 (CNA: VulnCheck; technical-description) - https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/ImageController.php#L159-L169 (CNA: VulnCheck; technical-description) - https://github.com/fishtankyu/bookstack-draft-image-idor-advisory.md (CNA: VulnCheck; third-party-advisory) - https://www.vulncheck.com/advisories/bookstack-before-26.09.3-incorrect-authorization-via-image-and-drawio-endpoints (CNA: VulnCheck; third-party-advisory) - https://codeberg.org/bookstack/bookstack/commit/4fec06236cbfb314fd72c1b3614c7c50162fb41c (disclosure@vulncheck.com) - https://codeberg.org/bookstack/bookstack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 (disclosure@vulncheck.com) - https://codeberg.org/bookstack/bookstack/releases/tag/v26.09.3 (disclosure@vulncheck.com) - https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/DrawioImageController.php#L82-L92 (disclosure@vulncheck.com) - https://github.com/BookStackApp/BookStack/blob/v26.09.2/app/Uploads/Controllers/ImageController.php#L159-L169 (disclosure@vulncheck.com) - https://github.com/BookStackApp/BookStack/commit/926e16a23f346be47d44746d14cba40cb355cbe1 (disclosure@vulncheck.com) - https://github.com/BookStackApp/BookStack/releases/tag/v26.09.3 (disclosure@vulncheck.com) - https://github.com/fishtankyu/bookstack-draft-image-idor-advisory.md (disclosure@vulncheck.com) - https://www.bookstackapp.com/blog/bookstack-release-v26-09-3/ (disclosure@vulncheck.com) - https://www.vulncheck.com/advisories/bookstack-before-26.09.3-incorrect-authorization-via-image-and-drawio-endpoints (disclosure@vulncheck.com) ## Provenance - CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-126811; retrieved 2026-11-12; source updated 2026-11-12 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126811; retrieved 2026-11-12; source updated 2026-11-11 - FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-126811; retrieved 2026-11-12; source updated Not reported Revision: efe014e15b150386ab274af9472edcf88cf536e73711abc3b4c76fb7da9dcec7 Canonical: https://y2.dev/cve/CVE-2026-126811 ## Agent and API access Public CVE pages, Markdown, and JSON are free to read without an account or API key. - Public catalog: https://y2.dev/cve/index.json. 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