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Full vulnerability report · 2021
CVE-2021-25219High confidence

Lame cache can be abused to severely degrade resolver performance

ISC · BIND9

5.3MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
SSA-389290 · CSAF 2.0 · revision 1 · finalSiemens ProductCERTSSA-389290: Third-Party Component Vulnerabilities in SINEC INS
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SINEC INS
Summary
In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.
Remediation
Update to V1.0.1.1 or later version
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-12130

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

What

In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → vulnerable operation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration.
CWE not yet assigned
CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticated
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

CERT-FR · French · CERTFR-2025-AVI-0756Multiples vulnérabilités dans les produits VMware

ve.org/CVERecord?id=CVE-2021-2429 Référence CVE CVE-2021-2437 https://www.cve.org/CVERecord?id=CVE-2021-2437 Référence CVE CVE-2021-2440 https://www.cve.org/CVERecord?id=CVE-2021-2440 Référence CVE CVE-2021-2441 https://www.cve.org/CVERecord?id=CVE-2021-2441 Référence CVE CVE-2021-2444 https://www.cve.org/CVERecord?id=CVE-2021-2444 Référence CVE CVE-2021-2478 https://www.cve.org/CVERecord?id=CVE-2021-2478 Référence CVE CVE-2021-2479 https://www.cve.org/CVERecord?id=CVE-2021-2479 Référence CVE CVE-2021-2481 https://www.cve.org/CVERecord?id=CVE-2021-2481 Référence CVE CVE-2021-25214 https://www.cve.org/CVERecord?id=CVE-2021-25214 Référence CVE CVE-2021-25219 https://www.cve.org/CVERecord?id=CVE-2021-25219 Référence CVE CVE-2021-25220 https://www.cve.org/CVERecord?id=CVE-2021-25220 Référence CVE CVE-2021-27645 https://www.cve.org/CVERecord?id=CVE-2021-27645 Référence CVE CVE-2021-32256 https://www.cve.org/CVERecord?id=CVE-2021-32256 Référence CVE CVE-2021-3236 https://www.cve.org/CVERecord?id=CVE-2021-3236 Référence CVE CVE-2021-3326 https://www.cve.org/CVERecord?id=CVE-2021-3326 Référence CVE CVE-2021-33294 https://www.cve.org/CVERecord?id=CVE-2021-33294 Référence CVE CVE-2021-33574 https://www.cve.org/CVERecord?id=CVE-2021-33574 Référence CVE CVE-2021-3421 https://www.cve.org/CVERecord?id=CVE-2

Official advisory
CERT-FR · French · CERTFR-2022-AVI-216Multiples vulnérabilités dans les produits Siemens

d?id=CVE-2021-25174 Référence CVE CVE-2021-25175 https://www.cve.org/CVERecord?id=CVE-2021-25175 Référence CVE CVE-2021-25176 https://www.cve.org/CVERecord?id=CVE-2021-25176 Référence CVE CVE-2021-25177 https://www.cve.org/CVERecord?id=CVE-2021-25177 Référence CVE CVE-2021-25178 https://www.cve.org/CVERecord?id=CVE-2021-25178 Référence CVE CVE-2021-25214 https://www.cve.org/CVERecord?id=CVE-2021-25214 Référence CVE CVE-2021-25215 https://www.cve.org/CVERecord?id=CVE-2021-25215 Référence CVE CVE-2021-25216 https://www.cve.org/CVERecord?id=CVE-2021-25216 Référence CVE CVE-2021-25217 https://www.cve.org/CVERecord?id=CVE-2021-25217 Référence CVE CVE-2021-25219 https://www.cve.org/CVERecord?id=CVE-2021-25219 Référence CVE CVE-2021-27290 https://www.cve.org/CVERecord?id=CVE-2021-27290 Référence CVE CVE-2021-31344 https://www.cve.org/CVERecord?id=CVE-2021-31344 Référence CVE CVE-2021-31346 https://www.cve.org/CVERecord?id=CVE-2021-31346 Référence CVE CVE-2021-31784 https://www.cve.org/CVERecord?id=CVE-2021-31784 Référence CVE CVE-2021-31889 https://www.cve.org/CVERecord?id=CVE-2021-31889 Référence CVE CVE-2021-31890 https://www.cve.org/CVERecord?id=CVE-2021-31890 Référence CVE CVE-2021-32803 https://www.cve.org/CVERecord?id=CVE-2021-32803 Référence CVE CVE-2021-32804 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2021-AVI-838Vulnérabilité dans les produits Synology

Une vulnérabilité a été découverte dans les produits Synology. Elle permet à un attaquant de provoquer un déni de service à distance.

Official advisory
CERT-FR · French · CERTFR-2021-AVI-828Vulnérabilité dans ISC BIND

Une vulnérabilité a été découverte dans ISC BIND. Elle permet à un attaquant de provoquer un déni de service à distance.

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
SINEC INS
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Update to V1.0.1.1 or later version
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 27 Oct 2021 · Last source change 16 Sept 2024, 17:33 UTC · CWE not yet assigned

CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-12130
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceUnavailable
NVD statusNVD modified after enrichment

Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-12130↗Patch or update reference↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-25219 · cve.blacktree.nl