CVE-2021-23017
nginx: Off-by-one in ngx_resolver_copy() when labels are followed by a pointer to a root domain name
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · May 25, 2021
Updated · August 4, 2026
Description
A flaw was found in nginx. An off-by-one error while processing DNS responses allows a network attacker to write a dot character out of bounds in a heap allocated buffer which can allow overwriting the least significant byte of next heap chunk metadata likely leading to a remote code execution in certain circumstances. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE-193 · Off-by-one Error