CVE-2025-40775 | DNS message with invalid TSIG causes an assertion failure

When an incoming DNS protocol message includes a Transaction Signature (TSIG), BIND always checks it. If the TSIG contains an invalid value in the algorithm field, BIND immediately aborts with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.8 and 9.21.0 through 9.21.7.

Published: 2025-05-21 Last update: 2026-04-15 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-40775 is rated Moderate Risk (44/100): CVSS High severity, with low exploitation likelihood (EPSS 0.18%). 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-2025-40775

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 2026-04-08 0.14% 0.18% +0.04%
2 2026-03-17 0.02% 0.14% +0.12%
3 2025-11-21 — 0.02% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-40775

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-2025-40775

OS Trackers for CVE-2025-40775

vendor priority summary link
alpine high CVE-2025-40775: 1 source package rows (bind); 6 state rows across 6 repos (3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 6, open 0. https://security.alpinelinux.org/vuln/CVE-2025-40775
debian unimportant CVE-2025-40775 unimportant 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-2025-40775
redhat high — https://access.redhat.com/security/cve/CVE-2025-40775
suse high CVE-2025-40775 severity important: SUSE including 53 source package names (5.1.0.6.40:bind-utils-9.20.9-150700.3.3.1, bind, …), 258 product×package rows across 77 product lines (Container suse/multi-linux-manager/5.1/x86_64/server, Image SLES15-SP7-Azure-3P, … (77 product lines)): Known Not Affected 195, Fixed 63. https://www.suse.com/security/cve/CVE-2025-40775/
ubuntu medium CVE-2025-40775 medium priority: Ubuntu including 3 source packages (bind9, bind9-libs, isc-dhcp), 24 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, trusty, upstream, xenial): not-affected 16, DNE 3, released 3, needs-triage 2. https://ubuntu.com/security/CVE-2025-40775

Affected software / configurations for CVE-2025-40775

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-40775

cvelogic Threat Intelligence