# CVE-2026-79663: Ech0 before 4.7.3 Stored XSS via RSS feed tag names

> Attackers with admin privileges can inject malicious scripts into RSS feed tag names, executing JavaScript in subscribers' RSS readers.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** GHSA-3v85-fqvh-7rxf, GHSA-9277-65xq-8gww, GO-2026-5100

## What is CVE-2026-79663?

CVE-2026-79663 is a medium-severity cross-site scripting vulnerability in lin-snow Ech0, published on 25 Aug 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

Ech0 before 4.7.3 contains a stored cross-site scripting vulnerability in the public RSS feed where tag names and markdown content are rendered without HTML escaping. Attackers with admin privileges can inject malicious tag names or raw HTML in echo content that executes as JavaScript in RSS readers that render HTML-type summaries, affecting anonymous subscribers and other users.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-79663?

3 open source packages ship an affected version, including github.com/lin-snow/Ech0 and github.com/lin-snow/ech0.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/lin-snow/Ech0` | Go | All versions | 1.4.8-0.20260503035519-fd320fe3e902 |
| `github.com/lin-snow/Ech0` | Go | All versions | 1.4.8-0.20260503035519-fd320fe3e902 |
| `github.com/lin-snow/ech0` | Go | All versions | 1.4.8-0.20260503035519-fd320fe3e902 |

## How do I fix CVE-2026-79663?

Upgrade github.com/lin-snow/Ech0 to 1.4.8-0.20260503035519-fd320fe3e902 or later.

## Is CVE-2026-79663 being exploited?

There is no known exploitation of CVE-2026-79663 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-79663 and fix it if it is affected.

What it is: CVE-2026-79663 is a medium-severity cross-site scripting vulnerability in lin-snow Ech0, published on 25 Aug 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-79663 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/lin-snow/Ech0 (Go): affected all versions; fixed in 1.4.8-0.20260503035519-fd320fe3e902
- github.com/lin-snow/Ech0 (Go): affected all versions; fixed in 1.4.8-0.20260503035519-fd320fe3e902
- github.com/lin-snow/ech0 (Go): affected all versions; fixed in 1.4.8-0.20260503035519-fd320fe3e902

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-2026-79663/ (Markdown: https://insights.sbomify.com/CVE-2026-79663/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-79663
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-79663
- OSV: https://osv.dev/vulnerability/CVE-2026-79663

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-79663/
Summaries are generated and may contain mistakes; the official description above is the record.