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CVE Record

CVE-2021-23133: Linux Kernel sctp_destroy_sock race condition

A race condition in Linux kernel SCTP sockets (net/sctp/socket.c) before 5.12-rc8 can lead to kernel privilege escalation from the context of a network service or an unprivileged process. If sctp_destroy_sock is called without sock_net(sk)->sctp.addr_wq_lock then an element is removed from the auto_asconf_splist list without any proper locking. This can be exploited by an attacker with network service privileges to escalate to root or from the context of an unprivileged user directly if a BPF_CGROUP_INET_SOCK_CREATE is attached which denies creation of some SCTP socket.

MediumCVSS 6.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-23133 is a Linux kernel race condition in SCTP socket cleanup. A local attacker, or a compromised network service running with enough privileges, may be able to escalate to root. The sources describe affected Linux kernels before 5.12-rc8 and distribution advisories, but do not show CISA KEV listing or active exploitation evidence.

Executive priority

Treat as a scheduled priority for Linux fleet patching, not an emergency internet-facing bug. The business risk is root-level compromise after local access or service compromise, so focus first on shared systems, high-value servers, and environments with untrusted local code.

Technical view

The flaw is improper locking around sctp_destroy_sock in net/sctp/socket.c. An entry can be removed from auto_asconf_splist without holding sock_net(sk)->sctp.addr_wq_lock, creating a race. The CVSS vector is local, low complexity, high privileges required, no user interaction, with high confidentiality, integrity, and availability impact.

Likely exposure

Exposure is most likely on Linux systems running kernels before the upstream 5.12-rc8 fix, especially where SCTP sockets are available. The provided sources do not enumerate all affected distribution kernel builds, so asset owners should map exposure through their vendor kernel advisories.

Exploitation context

The sources describe privilege escalation from a network service context, or from an unprivileged process when a BPF_CGROUP_INET_SOCK_CREATE program denies some SCTP socket creation. CISA KEV is false in the bundle, and no cited source confirms active exploitation.

Researcher notes

The upstream issue centers on missing addr_wq_lock protection during auto_asconf_splist removal in sctp_destroy_sock. The source bundle does not provide a complete affected-version matrix beyond kernels before 5.12-rc8, so distribution backport status must be verified per vendor advisory.

Mitigation direction

  • Apply Linux kernel updates from the operating system or appliance vendor.
  • Prioritize systems allowing local users, multi-tenant workloads, or exposed network services.
  • Review Fedora, Debian, NetApp, or applicable vendor advisories for fixed package versions.
  • If immediate patching is blocked, check vendor guidance for supported temporary mitigations.

Validation and detection

  • Inventory Linux kernel versions and compare them with vendor-fixed releases.
  • Confirm whether SCTP functionality is available on relevant hosts.
  • Identify systems using BPF_CGROUP_INET_SOCK_CREATE policies affecting SCTP socket creation.
  • Verify patched systems no longer run vulnerable kernel builds.
  • Track remediation through package manager or configuration management evidence.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-362: Exact CWE lookup

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description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-23133 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
9Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6.7CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H0.85.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.7Medium
CVSS 3.1 vector shape for CVE-2021-23133Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Linux KernelLinux KernelunspecifiedListed
Weakness

CWE details

CWE-362

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-362 · source CWE mapping

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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