# CVE-2026-52792: Algernon: Server-side script source disclosure on Windows via NTFS filename

> Unauthenticated attackers can retrieve raw source code of server-side scripts on Windows by exploiting NTFS filename aliases, potentially exposing credentials and session secrets.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-mm6c-5j6x-hq8m, GO-2026-5903

## What is CVE-2026-52792?

CVE-2026-52792 is a high-severity vulnerability in xyproto algernon, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Algernon is a small self-contained pure-Go web server. Prior to 1.17.9, Algernon on Windows selects a file handler in engine/handlers.go by calling filepath.Ext() without first rejecting NTFS-equivalent names such as x.lua::$DATA, x.lua., and x.lua . An unauthenticated client can append one of these suffixes to a public server-side script using the .lua, .tl, .po2, .amber, or .frm extension. The request path passes through URL2filename in utils/files.go, skips the renderer and execution cases, and reaches FilePage, os.Open, ReadAndLogErrors, and ToClient, while NTFS resolves the alias to the underlying script. The server consequently returns raw script source and can expose database credentials, API keys, and the SetCookieSecret value, which may permit forged session cookies. Linux and macOS hosts are not affected by this issue. This issue is fixed in version 1.17.9.

Weakness: CWE-69 (Improper Handling of Windows ::DATA Alternate Data Stream)

## Which versions are affected by CVE-2026-52792?

3 open source packages ship an affected version, including github.com/xyproto/algernon.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/xyproto/algernon` | Go | All versions | 1.17.9 |
| `github.com/xyproto/algernon` | Go | All versions | 1.17.9 |
| `github.com/xyproto/algernon` | Go | All versions | 1.17.9 |

## How do I fix CVE-2026-52792?

Upgrade github.com/xyproto/algernon to 1.17.9 or later.

## Is CVE-2026-52792 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52792 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52792 and fix it if it is affected.

What it is: CVE-2026-52792 is a high-severity vulnerability in xyproto algernon, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52792 exists.

Affected packages and fixed versions:
- github.com/xyproto/algernon (Go): affected all versions; fixed in 1.17.9
- github.com/xyproto/algernon (Go): affected all versions; fixed in 1.17.9
- github.com/xyproto/algernon (Go): affected all versions; fixed in 1.17.9

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-52792/ (Markdown: https://insights.sbomify.com/CVE-2026-52792/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52792
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52792
- OSV: https://osv.dev/vulnerability/CVE-2026-52792

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52792/
Summaries are generated and may contain mistakes; the official description above is the record.