Red Hat Software Collections update for rh-nginx116-nginx

Published: 2021-06-09
Risk High
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2021-23017
Exploitation vector Network
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
Red Hat Software Collections
Universal components / Libraries / Software for developers

rh-nginx116-nginx (Red Hat package)
Operating systems & Components / Operating system package or component

Vendor Red Hat Inc.

Security Advisory

This security advisory describes one high risk vulnerability.

1) Off-by-one

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] [PCI]

CVE-ID: CVE-2021-23017

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

Exploit availability: Yes


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.


Install updates from vendor's website.

Vulnerable software versions

Red Hat Software Collections: 1 for RHEL 7, 1 for RHEL 7.7

rh-nginx116-nginx (Red Hat package): before 1.16.1-6.el7

CPE 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. However, proof of concept for this vulnerability is available.