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CVE Record

CVE-2025-21638: sctp: sysctl: auth_enable: avoid using current->nsproxy

In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: auth_enable: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'net' structure can be obtained from the table->data using container_of(). Note that table->data could also be used directly, but that would increase the size of this fix, while 'sctp.ctl_sock' still needs to be retrieved from 'net' structure.

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel flaw in SCTP authentication settings can dereference missing process namespace data, causing a kernel fault. A locally authenticated, low-privilege user may be able to disrupt an affected system. The supplied CVSS 3.1 score is 7.1, with potential high integrity and availability impact but no stated confidentiality impact.

Executive priority

Prioritize remediation on shared Linux infrastructure and systems where less-trusted users or workloads can execute locally. This is high severity but not evidenced as remotely exploitable or actively exploited. Handle through the normal expedited kernel-patching process, with faster treatment for critical multi-tenant hosts and exposed operational appliances.

Technical view

The SCTP auth_enable sysctl handler incorrectly obtained network-namespace state through current->nsproxy. That pointer can be NULL while a task exits, producing a null-pointer dereference and kernel Oops. The upstream correction derives the appropriate network namespace from the sysctl table data, avoiding dependence on the currently executing task.

Likely exposure

Exposure requires an affected Linux kernel and local low-privileged access; no user interaction is required. The supplied affected-version data contains commit identifiers and ambiguous version entries, so organizations should determine status using their distribution or product vendor's advisory rather than relying solely on version-string comparisons.

Exploitation context

The bundle identifies a syzbot-discovered failure involving an exiting task and acct(2). It provides no evidence of public weaponization or attacks in the wild, and the CVE is not listed as KEV. Treat this as a meaningful local denial-of-service or integrity risk, not a demonstrated remote compromise path.

Researcher notes

The failure is a namespace-lifetime/context error in the SCTP sysctl path. The supplied CVSS vector is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H. Source evidence directly supports a NULL dereference and kernel Oops; it does not explain a reliable integrity-impact mechanism. Exact affected ranges require vendor interpretation because the bundled version representation is unclear.

Mitigation direction

  • Install a vendor-supported kernel update containing the referenced upstream stable correction.
  • Review applicable Linux distribution or product advisories for the precise fixed package version.
  • Prioritize multi-user, shared-hosting, container-host, and appliance systems permitting untrusted local activity.
  • If updating is delayed, follow vendor-provided compensating guidance; none is specified in the bundle.

Validation and detection

  • Inventory running kernels and installed kernel packages across Linux hosts and appliances.
  • Compare each kernel against its distribution or product vendor's CVE-2025-21638 advisory.
  • Confirm the updated kernel is running after installation and any required reboot.
  • Review kernel logs for SCTP-related Oops or null-pointer dereference events.
  • Verify scanners recognize vendor backports instead of relying only on upstream version numbers.
Prepared
Confidence
medium
Sources
6

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.

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CVE-2025-21638 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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
3Timeline events
2ADP providers
11Source 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
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H1.85.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.1High
CVSS 3.1 vector shape for CVE-2025-21638Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxb14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, b14878ccb7fac0242db82720b784ab62c467c0dc, e5eae4a0511241959498b180fa0df0d4f1b11b9c, 88830f227a1f96e44d82ddfcb0cc81d517ec6dd8, 3938b0336a93fa5faa242dc9e5823ac69df9e066, 3.10.41, 3.12.21, 3.14.5unaffected
LinuxLinux3.15, 0, 5.4.292, 5.10.234, 5.15.177, 6.1.125, 6.6.72, 6.12.10, 6.13affected
Weakness

CWE details

No CWE listed

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