Date: Wed, 21 Jul 2021 09:15:24 +0200 (CEST) From: Daniel Stenberg <daniel@...x.se> To: curl security announcements -- curl users <curl-users@...l.haxx.se>, curl-announce@...l.haxx.se, libcurl hacking <curl-library@...l.haxx.se>, oss-security@...ts.openwall.com Subject: [SECURITY ADVISORY] curl: TELNET stack contents disclosure again TELNET stack contents disclosure again ====================================== Project curl Security Advisory, July 21st 2021 - [Permalink](https://curl.se/docs/CVE-2021-22925.html) VULNERABILITY ------------- 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. We are not aware of any exploit of this flaw. INFO ---- This flaw has existed in curl since commit [a1d6ad2610](https://github.com/curl/curl/commit/a1d6ad2610) in libcurl 7.7, released on March 22, 2001. There was a previous attempt to fix this issue in curl 7.77.0 but it was not done proper. The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2021-22925 to this issue. CWE-457: Use of Uninitialized Variable Severity: Medium AFFECTED VERSIONS ----------------- - Affected versions: curl 7.7 to and including 7.77.0 - Not affected versions: curl < 7.7 and curl >= 7.78.0 Also note that libcurl is used by many applications, and not always advertised as such. THE SOLUTION ------------ Use sscanf() properly and only use properly filled-in buffers. A [fix for CVE-2021-22925](https://github.com/curl/curl/commit/894f6ec730597eb243618d33cc84d71add8d6a8a) RECOMMENDATIONS -------------- A - Upgrade curl to version 7.78.0 B - Apply the patch to your local version C - Avoid using `CURLOPT_TELNETOPTIONS` TIMELINE -------- This issue was reported to the curl project on June 11, 2021. This advisory was posted on July 21, 2021. CREDITS ------- This issue was reported and patched by Red Hat Product Security. Thanks a lot! -- / daniel.haxx.se | Commercial curl support up to 24x7 is available! | Private help, bug fixes, support, ports, new features | https://www.wolfssl.com/contact/
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