CVE-2021-43389: There is an array-index-out-of-bounds flaw in the detach_capi_ctr function in drivers/isdn/capi/kcapi.c

Ubuntu release	Source package	Vendor state	Fixed version	Evidence
Ubuntu 24.04 LTSnoble · standard archive	`linux-raspi-realtime`	Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.	`Not published in this feed`	Canonical record ↗Source updated 9 Sept 2026

Recommended actionWithin 7 days

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available

What, why and how

An issue was discovered in the Linux kernel before 5.14.15. There is an array-index-out-of-bounds flaw in the detach_capi_ctr function in drivers/isdn/capi/kcapi.c.

What

An issue was discovered in the Linux kernel before 5.14.15. There is an array-index-out-of-bounds flaw in the detach_capi_ctr function in drivers/isdn/capi/kcapi.c.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

An issue was discovered in the Linux kernel before 5.14.15. There is an array-index-out-of-bounds flaw in the detach_capi_ctr function in drivers/isdn/capi/kcapi.c.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

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.

Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path: local access → Out-of-bounds Read → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface: Local
Privileges required: Low: a basic authenticated account is required
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: a standard category for the underlying weakness.: CWE-125 ↗
CWE-125: Out-of-bounds Read. The product reads data past the end, or before the beginning, of the intended buffer.
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level 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.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land: The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.

CWE-125Public exploit reference

Official authority intelligence

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

ENISA EUVD · EUVD-2021-30324Official EUVD mapping

0 linked advisory records.

Official EUVD record

BSI · German · WID-SEC-W-2022-0228Linux Kernel: Schwachstelle ermöglicht Denial of Service

Ein lokaler Angreifer kann eine Schwachstelle im Linux Kernel ausnutzen, um einen Denial of Service zu verursachen.

There is an array-index-out-of-bounds flaw in the detach_capi_ctr function in drivers/isdn/capi/kcapi.c

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

EUVD-2021-30324

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance

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