Red Hat Enterprise Linux 8 update for the nginx:1.20 module
| Risk | High |
| Patch available | YES |
| Number of vulnerabilities | 1 |
| CVE-ID | CVE-2021-23017 |
| CWE-ID | CWE-193 |
| Exploitation vector | Network |
| Public exploit | Public exploit code for vulnerability #1 is available. |
| Vulnerable software |
Red Hat Enterprise Linux for ARM 64 Operating systems & Components / Operating system Red Hat Enterprise Linux for Power, little endian Operating systems & Components / Operating system Red Hat Enterprise Linux for IBM z Systems Operating systems & Components / Operating system Red Hat Enterprise Linux for x86_64 Operating systems & Components / Operating system |
| Vendor | Red Hat Inc. |
Security Bulletin
This security bulletin contains one high risk vulnerability.
1) Off-by-one
EUVDB-ID: #VU53543
Risk: High
CVSSv4.0: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Amber]
CVE-ID: CVE-2021-23017
CWE-ID:
CWE-193 - Off-by-one Error
Exploit availability: Yes
DescriptionThe 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.
MitigationInstall updates from vendor's website.
Red Hat Enterprise Linux for ARM 64: 8
Red Hat Enterprise Linux for Power, little endian: 8
Red Hat Enterprise Linux for IBM z Systems: 8
Red Hat Enterprise Linux for x86_64: 8.0
CPE2.3- cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_arm_64:8:*:*:*:*:red_hat_enterprise_linux:*:*
- cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_little_endian:8:*:*:*:*:red_hat_enterprise_linux:*:*
- cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_ibm_z_systems:8:*:*:*:*:red_hat_enterprise_linux:*:*
- cpe:2.3:o:red_hat:red_hat_enterprise_linux:8.0:*:*:*:*:*:*:*
https://access.redhat.com/errata/RHSA-2022:0323
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.
