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CVE Record

CVE-2024-38538: net: bridge: xmit: make sure we have at least eth header len bytes

In the Linux kernel, the following vulnerability has been resolved: net: bridge: xmit: make sure we have at least eth header len bytes syzbot triggered an uninit value[1] error in bridge device's xmit path by sending a short (less than ETH_HLEN bytes) skb. To fix it check if we can actually pull that amount instead of assuming. Tested with dropwatch: drop at: br_dev_xmit+0xb93/0x12d0 [bridge] (0xffffffffc06739b3) origin: software timestamp: Mon May 13 11:31:53 2024 778214037 nsec protocol: 0x88a8 length: 2 original length: 2 drop reason: PKT_TOO_SMALL [1] BUG: KMSAN: uninit-value in br_dev_xmit+0x61d/0x1cb0 net/bridge/br_device.c:65 br_dev_xmit+0x61d/0x1cb0 net/bridge/br_device.c:65 __netdev_start_xmit include/linux/netdevice.h:4903 [inline] netdev_start_xmit include/linux/netdevice.h:4917 [inline] xmit_one net/core/dev.c:3531 [inline] dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3547 __dev_queue_xmit+0x34db/0x5350 net/core/dev.c:4341 dev_queue_xmit include/linux/netdevice.h:3091 [inline] __bpf_tx_skb net/core/filter.c:2136 [inline] __bpf_redirect_common net/core/filter.c:2180 [inline] __bpf_redirect+0x14a6/0x1620 net/core/filter.c:2187 ____bpf_clone_redirect net/core/filter.c:2460 [inline] bpf_clone_redirect+0x328/0x470 net/core/filter.c:2432 ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2238 bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline] __bpf_prog_run include/linux/filter.h:657 [inline] bpf_prog_run include/linux/filter.h:664 [inline] bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425 bpf_prog_test_run_skb+0x14ea/0x1f20 net/bpf/test_run.c:1058 bpf_prog_test_run+0x6b7/0xad0 kernel/bpf/syscall.c:4269 __sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5678 __do_sys_bpf kernel/bpf/syscall.c:5767 [inline] __se_sys_bpf kernel/bpf/syscall.c:5765 [inline] __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5765 x64_sys_call+0x96b/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2024-38538 is a Linux kernel bridge networking flaw. A malformed, too-short network buffer could reach the bridge transmit path and trigger use of uninitialized data. The public sources show a kernel fix and Debian LTS notice, but do not provide CVSS, confirmed exploitation, or business-impact details.

Executive priority

Treat this as a kernel maintenance item for bridge-heavy environments, not as an emergency internet-facing incident based on current evidence. Prioritize patch verification on container, virtualization, and network infrastructure hosts because kernel networking bugs can have broad operational blast radius.

Technical view

The bug is in net/bridge/br_device.c br_dev_xmit. syzbot triggered KMSAN uninitialized-value reporting with an skb shorter than ETH_HLEN. The fix validates that the Ethernet header length can be pulled before proceeding, causing undersized packets to be dropped as PKT_TOO_SMALL.

Likely exposure

Exposure is most relevant to Linux systems using bridge networking, such as virtualization, container, or network-host roles. The provided trace involves BPF test-run and bridge transmit code, but the sources do not define required privileges, remote reachability, or exact exploit preconditions.

Exploitation context

CISA KEV status is false in the bundle, and no cited source states active exploitation. Evidence is from syzbot testing, not public in-the-wild exploitation. The public record does not establish exploitability beyond triggering the kernel bug condition.

Researcher notes

The key condition is an skb shorter than ETH_HLEN entering br_dev_xmit. The stack trace shows BPF test-run and clone redirect paths, but source evidence does not prove practical exploitation requirements. Validate by code/version mapping, not by attempting offensive reproduction.

Mitigation direction

  • Update Linux kernels to vendor releases containing the referenced stable fixes.
  • Check Debian LTS guidance if running affected Debian kernel packages.
  • Prioritize bridge-networking hosts over general workstations during assessment.
  • Monitor vendor advisories for distribution-specific fixed package versions.
  • Avoid direct wrangler-style assumptions; use only kernel or distribution guidance.

Validation and detection

  • Inventory Linux kernel versions across hosts and appliances.
  • Identify systems using Linux bridge networking or loaded bridge modules.
  • Map installed kernels against vendor advisories and stable fix commits.
  • Confirm patched hosts reject undersized bridge transmit buffers safely.
  • Record unknown exploitability where vendor severity data is absent.
Prepared
Confidence
medium
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.

ATT&CK lookup starting points

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CVE-2024-38538 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
11Source links

SSVC decision data

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

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
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 4.19.324, 5.4.286, 5.10.230, 5.15.172, 6.1.93, 6.6.33, 6.8.12, 6.9.3, 6.10affected
Weakness

CWE details

No CWE listed

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