Medium
TELNET stack contents disclosure again
Type: advisorySources: OSV
curl supports the `-t` command line option, known as `CURLOPT_TELNETOPTIONS` in libcurl. This rarely used option is used to send variable=content pairs to TELNET servers. Due to flaw in the option parser for sending `NEW_ENV` variables, libcurl could be made to pass on uninitialized data from a stack based buffer to the server. Therefore potentially revealing sensitive internal information to the server using a clear-text network protocol. This could happen because curl did not call and use `sscanf()` correctly when parsing the string provided by the application. The previous curl security vulnerability [CVE-2021-22898](https://curl.se/docs/CVE-2021-22898.html) is almost identical to this one but the fix was insufficient so this security vulnerability remained.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-22925
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:39 UTC · Revision 1
Source evidence
curl supports the `-t` command line option, known as `CURLOPT_TELNETOPTIONS` in libcurl. This rarely used option is used to send variable=content pairs to TELNET servers. Due to flaw in the option parser for sending `NEW_ENV` variables, libcurl could be made to pass on uninitialized data from a stack based buffer to the server. Therefore potentially revealing sensitive internal information to the server using a clear-text network protocol. This could happen because curl did not call and use `sscanf()` correctly when parsing the string provided by the application. The previous curl security vulnerability [CVE-2021-22898](https://curl.se/docs/CVE-2021-22898.html) is almost identical to this one but the fix was insufficient so this security vulnerability remained.
osv:CURL-CVE-2021-22925
Complete source record
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"id": "b6267f792b648a9222efd55736452c091845e107cd993f7b1563ca52acac46af",
"url": "https://osv.dev/vulnerability/CURL-CVE-2021-22925",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "TELNET stack contents disclosure again",
"summary": "curl supports the `-t` command line option, known as `CURLOPT_TELNETOPTIONS` in libcurl. This rarely used option is used to send variable=content pairs to TELNET servers. Due to flaw in the option parser for sending `NEW_ENV` variables, libcurl could be made to pass on uninitialized data from a stack based buffer to the server. Therefore potentially revealing sensitive internal information to the server using a clear-text network protocol. This could happen because curl did not call and use `sscanf()` correctly when parsing the string provided by the application. The previous curl security vulnerability [CVE-2021-22898](https://curl.se/docs/CVE-2021-22898.html) is almost identical to this one but the fix was insufficient so this security vulnerability remained.",
"evidence": "osv:CURL-CVE-2021-22925",
"products": [],
"severity": "medium",
"structured": {
"id": "CURL-CVE-2021-22925",
"aliases": [
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"modified": "2026-10-25T01:05:30.556980788Z",
"provider": "osv",
"references": [],
"provider_metadata": {
"CWE": {
"id": "CWE-457",
"desc": "Use of Uninitialized Variable"
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"URL": "https://curl.se/docs/CVE-2021-22925.json",
"www": "https://curl.se/docs/CVE-2021-22925.html",
"award": {
"amount": "800",
"currency": "USD"
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"issue": "https://hackerone.com/reports/1223882",
"affects": "both",
"package": "curl",
"severity": "Medium",
"last_affected": "7.77.0"
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"document_id": 444395,
"published_at": "2021-07-21T08:00:00+00:00"
}