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CVE-2025-40775

DNS message with invalid TSIG causes an assertion failure

High7.5EPSS 15.3%
Published
Updated
Reserved
Assigned by
isc

Description

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.

Scores

CVSS scores of CVE-2025-40775, by who scored it
Scored byCVSSScoreVector
iscCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Deferred3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
15.3% · top 3.2% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • ISC · BIND 9

    • affected 9.20.0 – ≤ 9.20.8
    • affected 9.21.0 – ≤ 9.21.7

What to do

Solution: Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.9 or 9.21.8.

Workaround: No workarounds known.

Exploitation: This flaw was discovered in internal testing. We are not aware of any active exploits.

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .