CVE-2024-40996

Kernel warning via oversized BPF write length

Published Jul 12, 2024 · Updated May 23, 2026

Improper BPF packet-length handling in Linux allows local users to trigger a kernel warning via crafted BPF programs. __bpf_try_make_writable passes an unsigned write_len above INT_MAX into skb_ensure_writable, causing pskb_may_pull_reason to emit a WARN backtrace instead of rejecting it first. The trigger requires local low-privileged access and CONFIG_DEBUG_NET; nondebug builds reject the oversized pull without a backtrace.

CVSS severity7.8
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper BPF packet-length handling in Linux allows local users to trigger a kernel warning via crafted BPF programs. __bpf_try_make_writable passes an unsigned write_len above INT_MAX into skb_ensure_writable, causing pskb_may_pull_reason to emit a WARN backtrace instead of rejecting it first. The trigger requires local low-privileged access and CONFIG_DEBUG_NET; nondebug builds reject the oversized pull without a backtrace.

The record

CVE
CVE-2024-40996
Published
Jul 12, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 12, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1b2b26595bb09febf14c5444c873ac4ec90a5a77 <7f9644782c559635bd676c12c59389a34ed7c866
  2. Affected versionversion=219eee9c0d16f1b754a8b85275854ab17df0850a <2bbe3e5a2f4ef69d13be54f1cf895b4658287080
  3. Affected versionversion=219eee9c0d16f1b754a8b85275854ab17df0850a <5e90258303a358e88737afb5048bee9113beea3a
  4. Affected versionversion=6.1.86 <6.1.96
  5. Affected versionversion=6.6.27 <6.6.36
  6. Affected versionversion=6.8.6 <6.9
  7. Affected versionversion=6.9
  8. Affected versionversion=8af60bb2b215f478b886f1d6d302fefa7f0b917d <dacc15e9cb248d19e5fc63c54bef0b9b55007761
  9. Affected versionversion=fff05b2b004d9a8a2416d08647f3dc9068e357c8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1b2b26595bb09febf14c5444c873ac4ec90a5a77 <7f9644782c559635bd676c12c59389a34ed7c866; version=219eee9c0d16f1b754a8b85275854ab17df0850a <2bbe3e5a2f4ef69d13be54f1cf895b4658287080; version=219eee9c0d16f1b754a8b85275854ab17df0850a <5e90258303a358e88737afb5048bee9113beea3a; version=6.1.86 <6.1.96; version=6.6.27 <6.6.36; version=6.8.6 <6.9; version=6.9; version=8af60bb2b215f478b886f1d6d302fefa7f0b917d <dacc15e9cb248d19e5fc63c54bef0b9b55007761; version=fff05b2b004d9a8a2416d08647f3dc9068e357c8

Published CVSS scores

7.8Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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