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CVE Record

CVE-2024-40909: bpf: Fix a potential use-after-free in bpf_link_free()

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix a potential use-after-free in bpf_link_free() After commit 1a80dbcb2dba, bpf_link can be freed by link->ops->dealloc_deferred, but the code still tests and uses link->ops->dealloc afterward, which leads to a use-after-free as reported by syzbot. Actually, one of them should be sufficient, so just call one of them instead of both. Also add a WARN_ON() in case of any problematic implementation.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel flaw can access a BPF link after it has been freed, potentially causing a crash or enabling a local low-privileged attacker to compromise confidentiality, integrity, and availability. The supplied CVSS score is 7.8. Exposure depends on the running kernel build and whether its vendor has backported the correction.

Executive priority

Treat as a high-priority kernel maintenance issue, especially on shared or multi-user Linux systems. It does not warrant an internet-wide emergency response based on supplied evidence, because exploitation requires local access and active exploitation is unconfirmed.

Technical view

After the deferred deallocation callback frees a bpf_link, bpf_link_free() could still inspect and invoke the ordinary deallocation callback through the freed object. The correction makes these callbacks mutually exclusive and adds a warning for problematic implementations. The issue was reported by syzbot.

Likely exposure

The CVSS vector requires local access and low privileges, without user interaction. Internet reachability alone does not establish exposure. The supplied version data is difficult to interpret reliably, so Linux systems should be evaluated using their exact kernel package and vendor backport status rather than version numbers alone.

Exploitation context

The source bundle does not list this CVE in CISA KEV and provides no evidence of active exploitation or a public weaponized exploit. A syzbot report supports the existence of the memory-safety bug, but does not establish malicious exploitation.

Researcher notes

The vulnerable sequence follows commit 1a80dbcb2dba: dealloc_deferred may free the link before later access to link->ops->dealloc. The patch selects only one deallocation path and adds WARN_ON validation. The bundle provides three stable-tree commits, suggesting branch-specific backports; confirm ancestry against the deployed kernel source.

Mitigation direction

  • Update to a vendor-supported kernel containing the applicable upstream stable correction or equivalent backport.
  • Check distribution security guidance for package-specific remediation and reboot requirements.
  • Prioritize multi-user systems where low-privileged local users can access affected kernel functionality.
  • Limit untrusted local access until the corrected kernel is installed, where operationally feasible.

Validation and detection

  • Inventory each host's running kernel version and distribution package build.
  • Verify the installed package contains an applicable listed fix commit or vendor-equivalent backport.
  • Confirm each remediated host is running the corrected kernel, not merely storing it on disk.
  • Review vendor advisories because the supplied affected-version data does not cleanly map distribution kernels.
Prepared
Confidence
medium
Sources
5

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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CVE-2024-40909 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/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
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2024-40909Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/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
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux876941f533e7b47fc69977fc4551c02f2d18af97, 1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce, 1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce, 5d8d447777564b35f67000e7838e7ccb64d525c8, 6.6.26, 6.8.5unaffected
LinuxLinux6.9, 0, 6.6.35, 6.9.6, 6.10affected
Weakness

CWE details

No CWE listed

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