CVE-2023-6516 | Specific recursive query patterns may lead to an out-of-memory condition

To keep its cache database efficient, `named` running as a recursive resolver occasionally attempts to clean up the database. It uses several methods, including some that are asynchronous: a small chunk of memory pointing to the cache element that can be cleaned up is first allocated and then queued for later processing. It was discovered that if the resolver is continuously processing query patterns triggering this type of cache-database maintenance, `named` may not be able to handle the cleanup events in a timely manner. This in turn enables the list of queued cleanup events to grow infinitely large over time, allowing the configured `max-cache-size` limit to be significantly exceeded. This issue affects BIND 9 versions 9.16.0 through 9.16.45 and 9.16.8-S1 through 9.16.45-S1.

Published: 2024-02-13 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-6516 is rated Moderate Risk (52.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.10%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-6516

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.18% 1.10% +0.92%
2 2025-11-21 0.63% 0.18% -0.45%
3 2025-11-18 — 0.63% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-6516

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-6516

OS Trackers for CVE-2023-6516

vendor priority summary link
alpine high CVE-2023-6516: 1 source package rows (bind); 7 state rows across 7 repos (3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2023-6516
debian not yet assigned CVE-2023-6516 not yet assigned priority: Debian including 1 source packages (bind9), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-6516
redhat high — https://access.redhat.com/security/cve/CVE-2023-6516
suse high CVE-2023-6516 severity important: SUSE including 340 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 960 product×package rows across 175 product lines (Image SLES15-SP3-BYOS-Azure, Image SLES15-SP3-BYOS-EC2-HVM, … (175 product lines)): Fixed 676, Known Affected 195, Known Not Affected 89. https://www.suse.com/security/cve/CVE-2023-6516/
ubuntu medium CVE-2023-6516 medium priority: Ubuntu including 3 source packages (bind9, bind9-libs, isc-dhcp), 30 status rows across 10 suites (bionic, focal, jammy, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 19, DNE 7, needs-triage 2, released 2. https://ubuntu.com/security/CVE-2023-6516

Affected software / configurations for CVE-2023-6516

Vendor Product Version Raw CPE
isc bind >= 9.16.0, <= 9.16.45 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind 9.16.8 cpe:2.3:a:isc:bind:9.16.8:s1:*:*:supported_preview:*:*:*
isc bind 9.16.11 cpe:2.3:a:isc:bind:9.16.11:s1:*:*:supported_preview:*:*:*
isc bind 9.16.12 cpe:2.3:a:isc:bind:9.16.12:s1:*:*:supported_preview:*:*:*
isc bind 9.16.13 cpe:2.3:a:isc:bind:9.16.13:s1:*:*:supported_preview:*:*:*
isc bind 9.16.14 cpe:2.3:a:isc:bind:9.16.14:s1:*:*:supported_preview:*:*:*
isc bind 9.16.21 cpe:2.3:a:isc:bind:9.16.21:s1:*:*:supported_preview:*:*:*
isc bind 9.16.32 cpe:2.3:a:isc:bind:9.16.32:s1:*:*:supported_preview:*:*:*
isc bind 9.16.36 cpe:2.3:a:isc:bind:9.16.36:s1:*:*:supported_preview:*:*:*
isc bind 9.16.43 cpe:2.3:a:isc:bind:9.16.43:s1:*:*:supported_preview:*:*:*
isc bind 9.16.45 cpe:2.3:a:isc:bind:9.16.45:s1:*:*:supported_preview:*:*:*
netapp active_iq_unified_manager — cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*

References for CVE-2023-6516

cvelogic Threat Intelligence