CVE-2026-5950 | Unbounded resend loop in BIND 9 resolver

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Published: 2026-05-20 Last update: 2026-05-21 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-5950 is rated Low Risk (28.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.07%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

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-2026-5950

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 2026-05-22 0.04% 0.07% +0.03%
2 2026-05-21 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-5950

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L 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:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 1.4 [email protected]

Weakness enumeration for CVE-2026-5950

GitHub Security Advisory for CVE-2026-5950

GHSA-2pjm-rchf-gxmp · Severity: medium — An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad...

OS Trackers for CVE-2026-5950

vendor priority summary link
debian not yet assigned CVE-2026-5950 not yet assigned priority: Debian including 1 source packages (bind9), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2026-5950
redhat medium — https://access.redhat.com/security/cve/CVE-2026-5950
suse medium CVE-2026-5950 severity moderate: SUSE including 41 source package names (bind, bind-9.18.49-150600.3.24.1, …), 154 product×package rows across 21 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (21 product lines)): Known Not Affected 139, Fixed 9, First Fixed 6. https://www.suse.com/security/cve/CVE-2026-5950/
ubuntu medium CVE-2026-5950 medium priority: Ubuntu including 3 source packages (bind9, bind9-libs, isc-dhcp), 24 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): needs-triage 12, released 5, not-affected 4, DNE 3. https://ubuntu.com/security/CVE-2026-5950

Affected software / configurations for CVE-2026-5950

Vendor Product Version Raw CPE
isc bind >= 9.18.36, < 9.18.49 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind >= 9.20.8, < 9.20.23 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind >= 9.21.7, < 9.21.21 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*

References for CVE-2026-5950

cvelogic Threat Intelligence