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CVE Record

CVE-2019-11479: Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes.

Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2019-11479 is a Linux kernel networking flaw that can let a remote peer force inefficient TCP queue fragmentation. The likely business impact is service degradation or denial of service, not data theft or system takeover. It matters most for internet-facing Linux servers, network appliances, and products built on affected kernels.

Executive priority

Schedule remediation in normal vulnerability maintenance, with higher priority for public-facing or critical availability systems. This is not described as data compromise or active exploitation in the provided sources, but remote denial-of-service risk can still affect customer-facing services.

Technical view

The issue is a hard-coded Linux default MSS of 48 bytes, allowing much heavier fragmentation of TCP resend queues than intended. CVSS is 5.3 with network reachability, low attack complexity, no privileges, no user interaction, and low availability impact. Fixed stable kernels are 4.4.182, 4.9.182, 4.14.127, 4.19.52, and 5.1.11.

Likely exposure

Exposure is most likely where affected Linux kernels or vendor products using them accept remote TCP connections. The bundle names Linux kernel branches 4.4, 4.9, 4.14, 4.19, and 5.1, plus multiple downstream vendor advisories. Exact exposure depends on vendor backports, not only version strings.

Exploitation context

The source bundle does not show KEV listing or active exploitation evidence. The issue is remotely reachable and low complexity, but the documented impact is availability degradation. Treat it as a patch-management and resilience issue, especially for public services, rather than as confirmed active compromise activity.

Researcher notes

This maps to CWE-405 and excessive resource consumption. Important nuance: distribution kernels may be fixed by backport without matching upstream fixed version numbers. The provided evidence identifies affected branches, fixed stable releases, Red Hat and Ubuntu advisories, and no KEV status.

Mitigation direction

  • Apply vendor kernel updates or fixed stable releases listed for this CVE.
  • Prioritize internet-facing Linux systems and appliances handling untrusted TCP traffic.
  • Check Red Hat, Ubuntu, and product-vendor advisories for backported fixes.
  • Track embedded or appliance vendors that ship Linux-based networking stacks.
  • Use vendor guidance for any temporary mitigations not specified in this bundle.

Validation and detection

  • Inventory Linux kernel versions and vendor kernel package advisories across exposed assets.
  • Confirm fixes are present through vendor package metadata or fixed stable kernel baselines.
  • Review public-facing Linux services and appliances for affected kernel lineage.
  • Verify vulnerability scanner findings against vendor backport documentation.
  • Document exceptions where vendor guidance is unavailable or inconclusive.
Prepared
Confidence
high
Sources
11

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

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cwe · low confidence lookup

CWE-405: Exact CWE lookup

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cve · low confidence lookup

CVE-2019-11479 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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
24Source 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
5.3CVSS 3.0MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

5.3Medium
CVSS 3.0 vector shape for CVE-2019-11479Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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
LinuxLinux kernel4.4, 4.9, 4.14, 4.19, 5.1Listed
Weakness

CWE details

CWE-405

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

CWE-405 · source CWE mapping

Asymmetric Resource Consumption (Amplification)

Asymmetric Resource Consumption (Amplification) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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