CVE-2021-47236

Memory exhaustion via failed transmit skb expansion

Published May 21, 2024 · Updated May 11, 2026

Resource leak in cdc_eem in affected Linux kernel versions allows local users to exhaust memory through failed skb expansion. eem_tx_fixup returns NULL when skb_copy_expand fails but leaves the original socket buffer allocated, and usbnet_start_xmit cannot release it. Exploitation requires local access and USB EEM transmission activity; repeated failures can deplete kernel memory and interrupt the system.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource leak in cdc_eem in affected Linux kernel versions allows local users to exhaust memory through failed skb expansion. eem_tx_fixup returns NULL when skb_copy_expand fails but leaves the original socket buffer allocated, and usbnet_start_xmit cannot release it. Exploitation requires local access and USB EEM transmission activity; repeated failures can deplete kernel memory and interrupt the system.

The record

CVE
CVE-2021-47236
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=2.6.30
  2. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <05b2b9f7d24b5663d9b47427fe1555bdafd3ea02
  3. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <14184ec5c958b589ba934da7363a2877879204df
  4. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <1bcacd6088d61c0ac6a990d87975600a81f3247e
  5. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <81de2ed06df8b5451e050fe6a318af3263dbff3f
  6. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <b4f7a9fc9d094c0c4a66f2ad7c37b1dbe9e78f88
  7. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <c3b26fdf1b32f91c7a3bc743384b4a298ab53ad7
  8. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <f12554b0ff639e74612cc01b3b4a049e098d2d65
  9. Affected versionversion=9f722c0978b04acba209f8ca1896ad05814bc3a3 <f4e6a7f19c82f39b1803e91c54718f0d7143767d

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.30; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <05b2b9f7d24b5663d9b47427fe1555bdafd3ea02; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <14184ec5c958b589ba934da7363a2877879204df; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <1bcacd6088d61c0ac6a990d87975600a81f3247e; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <81de2ed06df8b5451e050fe6a318af3263dbff3f; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <b4f7a9fc9d094c0c4a66f2ad7c37b1dbe9e78f88; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <c3b26fdf1b32f91c7a3bc743384b4a298ab53ad7; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <f12554b0ff639e74612cc01b3b4a049e098d2d65; version=9f722c0978b04acba209f8ca1896ad05814bc3a3 <f4e6a7f19c82f39b1803e91c54718f0d7143767d

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499Endpoint Denial of Service

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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