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CVE Record

CVE-2025-39848: ax25: properly unshare skbs in ax25_kiss_rcv()

In the Linux kernel, the following vulnerability has been resolved: ax25: properly unshare skbs in ax25_kiss_rcv() Bernard Pidoux reported a regression apparently caused by commit c353e8983e0d ("net: introduce per netns packet chains"). skb->dev becomes NULL and we crash in __netif_receive_skb_core(). Before above commit, different kind of bugs or corruptions could happen without a major crash. But the root cause is that ax25_kiss_rcv() can queue/mangle input skb without checking if this skb is shared or not. Many thanks to Bernard Pidoux for his help, diagnosis and tests. We had a similar issue years ago fixed with commit 7aaed57c5c28 ("phonet: properly unshare skbs in phonet_rcv()").

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in the Linux kernel’s AX.25 KISS receive path can corrupt shared network-packet memory and crash the system. Risk is concentrated on systems that process AX.25 KISS traffic, commonly associated with amateur-radio networking. The supplied CVSS score is 8.8, but the sources provide no evidence of active exploitation.

Executive priority

Treat as a high-priority targeted kernel update for AX.25 or radio-network systems. Patch those systems promptly and validate backports. For systems without AX.25 KISS use, confirm configuration and schedule remediation through normal high-severity kernel maintenance. There is no supplied evidence requiring an emergency incident response solely for exploitation activity.

Technical view

ax25_kiss_rcv() may queue or modify a shared socket buffer without first unsharing it. This can leave skb->dev NULL and trigger a crash in __netif_receive_skb_core(); earlier kernels could experience other corruption. Linux stable fixes add proper buffer unsharing. The record lists affected Linux versions from 2.6.12 through 6.17, with fixed stable releases identified among the supplied references.

Likely exposure

Prioritize Linux hosts where AX.25 and KISS receive functionality is enabled or operationally used. General-purpose systems not using this path are less likely to reach the vulnerable code, although kernel version and configuration still require verification. The supplied version data is irregular, so distribution-specific package status should be treated as authoritative.

Exploitation context

The CVSS vector describes adjacent-network access, low complexity, no privileges, and no user interaction. The reported outcomes are kernel crash and possible corruption. CVE-2025-39848 is not marked as CISA KEV in the supplied data, and no cited source establishes active exploitation or a public exploit.

Researcher notes

The source attributes the root cause to mutation or queuing of a potentially shared skb in ax25_kiss_rcv(). A later regression made skb->dev NULL and produced a clear crash; earlier behavior could involve less obvious corruption. No CWE is assigned. The 8.8 confidentiality and integrity ratings exceed the concrete crash evidence, so broader impact should not be asserted without additional research.

Mitigation direction

  • Install a vendor-supported kernel containing the applicable Linux stable fix.
  • Consult the operating-system or appliance vendor advisory for exact fixed package versions.
  • If patching is delayed, disable unused AX.25 KISS functionality where operationally acceptable.
  • Prioritize exposed radio-network gateways and other systems actively processing AX.25 KISS traffic.

Validation and detection

  • Record each system’s running kernel build, distribution package version, and reboot status.
  • Determine whether AX.25 KISS receive functionality is configured or actively used.
  • Confirm the vendor kernel includes the applicable referenced stable commit or documented backport.
  • Check kernel logs for __netif_receive_skb_core crashes or related skb corruption symptoms.
  • Recheck exposure after updating by verifying the running kernel, not only the installed package.
Prepared
Confidence
high
Sources
12

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-2025-39848 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:A/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
2ADP providers
12Source 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
8.8CVSS 3.1HighCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H2.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2025-39848Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:A/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.

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.4.299, 5.10.243, 5.15.192, 6.1.151, 6.6.105, 6.12.46, 6.16.6, 6.17affected
Weakness

CWE details

No CWE listed

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