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CURL-CVE-2021-22898
No affected components available
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 check the return code from a
sscanf(command, "%127[^,],%127s") function invoke correctly, and would leave
the piece of the send buffer uninitialized for the value part if it was
provided longer than 127 bytes. The buffer used for this is 2048 bytes big and
the variable part of the variable=content pairs would be stored correctly
in the send buffer, making curl sending "interleaved" bytes sequences of stack
contents. A single curl TELNET handshake could then be made to send off a
total of around 1800 bytes of (non-contiguous) stack contents in this style:
[control byte]name[control byte]
stack contents
[control byte]name[control byte]
stack contents
...
An easy proof of concept command line looks like this:
curl telnet://example.com -tNEW_ENV=a,bbbbbb (256 'b's)
Measures severity based on intrinsic characteristics of the vulnerability, independent of environment.
No exploitation activity has been observed at this time. Continue routine monitoring.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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