#VU53587 Use of uninitialized variable in cURL

Published: 2021-05-26

Vulnerability identifier: #VU53587

Vulnerability risk: Medium

CVSSv3.1: 4.1 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-22898


Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Client/Desktop applications / Other client software

Vendor: curl.haxx.se


The vulnerability allows a remote attacker to gain access to sensitive information.

The vulnerability exists due to usage of uninitialized variable in code, responsible for processing TELNET requests when parsing NEW_ENV variables. A remote attacker can force the affected application to connect to a telnet server under attackers control and read up to 1800 bytes from the uninitialized memory on the libcurl client system.

Proof of concept:

curl telnet://example.com -tNEW_ENV=a,bbbbbb (256 'b's)

Install updates from vendor's website.

Vulnerable software versions

cURL: 7.7 - 7.76.1

External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

Latest bulletins with this vulnerability