Algernon: Single-file mode unconditionally enables debug mode

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-45728: 0.30% estimated exploitation activity in the next 30 days; percentile 23.08 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When Algernon is invoked with a single file path instead of a directory — the documented "quick demo" workflow (algernon foo.lua, algernon page.po2, algernon index.html, algernon mywebsite.alg) — singleFileMode is set to true and debugMode is forcibly enabled with no opt-out: debugMode activates the PrettyError renderer, which on any Lua or template error response dumps: 1. The absolute path of the file that errored (Filename field of the error template). 2. The complete byte contents of that file, HTML-escaped, with the offending line wrapped in <font style='color: red !important'…</font. 3. The exception or parser error text — which in turn often quotes additional file content (Pongo2 errors include surrounding template lines; Lua tracebacks include argument values). This response is served with HTTP 200 OK to whoever sent the request that triggered the error. There is no authentication, no rate limit specific to errors, no redaction, and no opt-out short of avoiding…

Published by the source

19 May 2026, 14:35 UTC

Last modified by the source

19 May 2026, 14:35 UTC

Source last checked

26 Oct 2026, 15:22 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fwqx-8365-9983

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# Patch Next advisory brief: CVE-2026-45728

Advisory: Algernon: Single-file mode unconditionally enables debug mode
IDs: CVE-2026-45728, GHSA-fwqx-8365-9983
Record: https://patchnext.com/advisories/cve-2026-45728 (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/xyproto/algernon 1.17.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/xyproto/algernon: affected <= 1.17.6; fixed in 1.17.7

## Suggested inspection (read-only)
- Go github.com/xyproto/algernon: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/xyproto/algernon.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fwqx-8365-9983 (GitHub-reviewed advisory GHSA-fwqx-8365-9983 lists affected ranges: Go github.com/xyproto/algernon >=0 <=1.17.6)

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