CVE-2021-25218
A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use
02 Description
A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use
03 Exploitation and scoring
- Exploitation
- Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.
- SSVC decision
- Not assessed by CISA
- EPSS probability
- 3.65% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 89.5% of scored records. A rank, not a probability.
- NVD base score
- 7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVD analysis status
- Modified. NVD last modified this record on 2026-06-17.
- Red Hat severity
- Important. Red Hat's rating for its own products, not a CVSS rating.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2021-08-18 18:20Z5 YR AGO
- Last updated
- 2024-09-17 03:07Z2 YR AGO
- Reserved
- 2021-01-15
- Assigning CNA
- isc
- Record state
- PUBLISHED
- Severity
- High (CVSS 7.5)
- CNA CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weaknesses
- CWE-617Reachable AssertionBase
- Data version
- 5.1
- Document digest
- 87267b922bfc06bd2ecf10f38237d0fc69bf903372babe14a98f4c7aa96469f9
05 Affected products
06 References
- kb.isc.orghttps://kb.isc.org/v1/docs/cve-2021-25218
- www.openwall.com[oss-security] 20210818 ISC has disclosed a vulnerability in BIND (CVE-2021-25218)http://www.openwall.com/lists/oss-security/2021/08/18/3
- www.openwall.com[oss-security] 20210820 August BIND maintenance releases contain a defect affecting servers using the map zone file format (was: A vulnerability in BIND (CVE-2021-25218) will be announced 18 August 2021)http://www.openwall.com/lists/oss-security/2021/08/20/2
- lists.fedoraproject.orgFEDORA-2021-fbb258debfhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/
- security.netapp.comhttps://security.netapp.com/advisory/ntap-20210909-0002/
07 Remediation
Upgrade to the patched release most closely related to your current version of BIND: BIND 9.16.20 BIND 9.17.17 BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers. BIND 9.16.20-S1
08 Fixed in
Arch Linux
- bind Fixed in 9.16.20-1
Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.
A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.