Remote code execution in IBM API Connect

1) Off-by-one

EUVDB-ID: #VU53543

Risk: High

CVSSv3.1: 7.3 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2021-23017

CWE-ID: CWE-193 - Off-by-one Error

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to an off-by-one error within the ngx_resolver_copy() function when processing DNS responses. A remote attacker can trigger an off-by-one error, write a dot character (‘.’, 0x2E) out of bounds in a heap allocated buffer and execute arbitrary code on the system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

The vulnerability can be triggered by a DNS response in reply to a DNS request from nginx when the resolver primitive is configured. A specially crafted packet allows overwriting the least significant byte of next heap chunk metadata with 0x2E.

Mitigation

Install update from vendor's website.

Vulnerable software versions

IBM API Connect: 5.0.0 - 5.0.8.11

External links

http://www.ibm.com/blogs/psirt/security-bulletin-ibm-api-connect-v5-is-impacted-by-a-vulnerability-in-nginx-cve-2021-23017/
http://www.ibm.com/support/pages/node/6483657

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to visit a specially crafted website or open a file.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.