# CVE-2026-121544: Koodo Reader through 2.4.6 Path Traversal via OPDS Cover and Download Handlers

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

Koodo Reader through 2.4.6 contains a path traversal vulnerability in the self-hosted HTTP server's OPDS handlers that allows authenticated attackers to read files outside the upload directory. Attackers can upload a crafted books.db with a cover value containing ../ sequences, then request /opds/cover/{key} to read files accessible to the server process.

## 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://github.com/koodo-reader/koodo-reader/commit/cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8

## Affected products and versions

- koodo-reader / koodo-reader (koodo-reader/koodo-reader): ≥ 0; ≤ 2.4.6 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 4.9 (medium); CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N; source: CNA: VulnCheck

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/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: 4.9 (medium); CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-22

## Exploit evidence

- exploit: https://github.com/koodo-reader/koodo-reader/issues/1654 (ADP: CISA-ADP)

## References

- https://github.com/koodo-reader/koodo-reader/issues/1654 (CNA: VulnCheck; issue-tracking)

- https://github.com/koodo-reader/koodo-reader (CNA: VulnCheck; product)

- https://github.com/koodo-reader/koodo-reader/commit/cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8 (CNA: VulnCheck; patch)

- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L167-L194 (CNA: VulnCheck; technical-description)

- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L384-L431 (CNA: VulnCheck; technical-description)

- https://github.com/koodo-reader/koodo-reader/compare/205539043b0a2afd9fd8bf99ef8434bd1833c2bf...cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/koodo-reader-through-2.4.6-path-traversal-via-opds-cover-and-download-handlers (CNA: VulnCheck; third-party-advisory)

- https://github.com/koodo-reader/koodo-reader/issues/1654 (ADP: CISA-ADP; exploit)

- https://github.com/koodo-reader/koodo-reader (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L167-L194 (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L384-L431 (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/commit/cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8 (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/compare/205539043b0a2afd9fd8bf99ef8434bd1833c2bf...cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8 (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/issues/1654 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/koodo-reader-through-2.4.6-path-traversal-via-opds-cover-and-download-handlers (disclosure@vulncheck.com)

- https://github.com/koodo-reader/koodo-reader/issues/1654 (134c704f-9b21-4f2e-91b3-4a467353bcc0)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121544; retrieved 2026-11-03; source updated 2026-11-03

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121544; retrieved 2026-11-03; source updated 2026-11-03

Revision: 8cc6694305642e680d2aa88113c5af12a7dcab97e2035519d096fc55010732cc

Canonical: https://y2.dev/cve/CVE-2026-121544

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