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CVE Record

CVE-2026-64055: net: ethernet: cortina: Carry over frag counter

In the Linux kernel, the following vulnerability has been resolved: net: ethernet: cortina: Carry over frag counter The gmac_rx() NAPI poll function assembles packets in an SKB from a ring buffer. If the ring buffer gets completely emptied during a poll cycle, we exit gmac_rx(), but the packet is not yet completely assembled in the SKB, yet the fragment counter frag_nr is reset to zero on the next invocation. Solve this by making the RX fragment counter a part of the port struct, and carry it over between invocations. Reset the fragment counter only right after calling napi_gro_frags(), on error (after calling napi_free_frags()) or if stopping the port. Reset it in some place where not strictly necessary just to emphasize what is going on. This was found by Sashiko during normal patch review.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-64055 is a critical Linux kernel networking flaw in the Cortina Ethernet GMAC receive path. A packet-fragment counter can be lost between receive polling cycles, leaving packets assembled with incorrect state. The public record rates potential confidentiality, integrity, and availability impact as high, but it does not describe active attacks.

Executive priority

Treat this as high-priority patch work for systems using the affected Linux networking driver, especially embedded, appliance, or edge systems. Do not assume broad fleet exposure without confirming driver use, but unresolved kernel networking flaws with CVSS 9.8 should enter expedited remediation.

Technical view

In gmac_rx(), NAPI polling builds an SKB from receive-ring fragments. If polling exits after emptying the ring before the packet is complete, frag_nr resets on the next invocation. The fix carries the fragment counter in the port structure and resets it only after GRO completion, error cleanup, or port stop.

Likely exposure

Exposure is likely limited to Linux systems running affected kernel versions with the Cortina Ethernet GMAC driver path enabled or in use. The source lists Linux as affected across multiple kernel version lines, but does not identify specific distributions, devices, or hardware models.

Exploitation context

The CVE is not listed as KEV in the provided bundle. No cited source states active exploitation, public exploit availability, or a weaponized technique. The network vector and high CVSS score justify urgency, but exploitability details are incomplete in the public record provided.

Researcher notes

The record attributes discovery to normal patch review, not incident response. The key technical question is whether malformed or fragmented receive traffic can reliably trigger memory safety or state corruption. Public sources do not provide a concrete exploit primitive, affected hardware list, or workaround beyond applying fixed kernel changes.

Mitigation direction

  • Update to a kernel containing the referenced stable fixes.
  • Use distribution or device-vendor kernel advisories for supported packages.
  • Backport the stable commit only if maintaining a custom kernel.
  • Prioritize assets using Cortina Ethernet GMAC networking.
  • If no patch is available, check vendor guidance for temporary controls.

Validation and detection

  • Inventory Linux kernels and compare versions against vendor-fixed packages.
  • Confirm whether the Cortina GMAC driver is built, loaded, or used.
  • Check kernel source or changelog for the referenced stable commits.
  • Retest network functions after patching to confirm driver stability.
  • Track CVE and vendor advisories for revised affected-version data.
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.

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CVE-2026-64055 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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
3Timeline 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
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2026-64055Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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

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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88, 4d5ae32f5e1e13f7f36d6439ec3257993b9f5b88unaffected
LinuxLinux4.16, 0, 5.10.258, 5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.18.34, 7.0.11, 7.1affected
Weakness

CWE details

No CWE listed

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