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CVE Record

CVE-2026-68137: net/x25: fix use-after-free in x25_kill_by_neigh()

In the Linux kernel, the following vulnerability has been resolved: net/x25: fix use-after-free in x25_kill_by_neigh() x25_kill_by_neigh() walks the global X.25 socket list looking for sockets attached to a terminating neighbour. x25_list_lock protects list membership while the lookup is in progress, but it does not pin a socket's lifetime after the lock is dropped. The function currently drops x25_list_lock before calling lock_sock(s). A concurrent close can run x25_release(), remove the same socket from x25_list, and drop the last socket reference in that window. The neighbour teardown path can then lock or inspect a freed struct sock/struct x25_sock. Take sock_hold(s) while x25_list_lock still proves that the list entry is live, then drop the temporary reference after the socket has been locked, rechecked, and released. Recheck x25_sk(s)->neighbour after lock_sock(), because another path may have disconnected the socket before this path acquired the socket lock. Restart the list walk after each disconnect because the list lock was dropped and the previous iterator state may no longer be valid. A QEMU/KASAN run against origin/master reproduced a slab-use-after-free in x25_kill_by_neigh().

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A race in Linux X.25 networking can leave the kernel using a socket after its memory has been freed. This may crash or corrupt affected systems and, according to the supplied CVSS assessment, could affect confidentiality, integrity, and availability. Exposure depends on running a vulnerable kernel and exercising X.25 networking.

Executive priority

Prioritize rapid assessment because the supplied rating is critical and the flaw affects kernel memory safety. Expedite remediation on X.25-using systems; handle other affected hosts through risk-based patching after confirming whether the vulnerable subsystem is reachable.

Technical view

During neighbour teardown, x25_kill_by_neigh() can release x25_list_lock without holding a socket reference. A concurrent x25_release() may remove and free that socket before the teardown path locks or inspects it. The stable fixes hold a temporary reference, recheck the neighbour after locking, and restart list traversal after disconnecting.

Likely exposure

Highest for systems running an affected Linux kernel with X.25 networking configured or exercised. Systems that do not use X.25 likely have substantially lower practical exposure, but the supplied sources do not provide deployment prevalence, configuration-specific reachability, or distribution package mappings.

Exploitation context

The issue was reproduced under QEMU with KASAN as a slab use-after-free. The supplied sources do not report exploitation in the wild, and the CVE is not listed as KEV. They also do not demonstrate reliable code execution or describe a public exploit.

Researcher notes

The confirmed primitive is a race-driven use-after-free involving socket lifetime and neighbour teardown. Reproduction used QEMU/KASAN, establishing the defect but not production exploitability. Exact branch exposure should be checked against the listed stable commits and vendor advisories because the supplied version list mixes release numbers and commit identifiers.

Mitigation direction

  • Update to a vendor-supported kernel containing the applicable listed stable fix.
  • Verify the selected distribution package backports the fix for CVE-2026-68137.
  • If immediate patching is impossible, assess whether X.25 can be disabled without operational impact.
  • Monitor Linux distribution and kernel guidance for revised affected-version information.

Validation and detection

  • Inventory kernel versions and identify systems where X.25 is configured, loaded, or operationally required.
  • Map each kernel branch to the corresponding stable fix commit or distribution advisory.
  • Confirm updated kernels are running after reboot, not merely installed.
  • In an authorized test environment, verify the reported KASAN condition no longer reproduces.
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

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CVE-2026-68137 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-2026-68137Attack 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
LinuxLinux5c94b6205e87411dbe9dc1ca088eb36b8837fb47, 409570a619c1cda2e0fde6018a256b9e3d3ba0ee, 7781607938c8371d4c2b243527430241c62e39c2, 7781607938c8371d4c2b243527430241c62e39c2, 7781607938c8371d4c2b243527430241c62e39c2, 7781607938c8371d4c2b243527430241c62e39c2, 7781607938c8371d4c2b243527430241c62e39c2, 7781607938c8371d4c2b243527430241c62e39c2, dffc859d1d9560da594e4282091781b8d2715f00, 858642789ada1b48630f322e59416ca9fca3e6b7, 4c240c5a105557e4546d0836e694868f22fd09b0, 9acf05b4e7b55fdb712ef7b331dbce5bcd391d0f, 4a279d7ee1c65411b4055ecd428b8aa2b1711c1f, 671529db75e6be777bb1c76aa07c2bdd2992be6d, 5.10.110, 5.15.33, 4.9.311, 4.14.276, 4.19.238, 5.4.189, 5.16.19, 5.17.2unaffected
LinuxLinux5.18, 0, 5.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101, 6.18.42, 7.1.6, 7.2affected
Weakness

CWE details

No CWE listed

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