CVE-2025-40204Network attack vector

SCTP authentication bypass via timing-leaky MAC comparison

Published Nov 12, 2025 · Updated Aug 5, 2026

Timing discrepancy in Linux kernel SCTP allows remote attackers to recover authentication MACs through network timing measurements. The COOKIE ECHO path in sctp_unpack_cookie and AUTH path in sctp_sf_authenticate use early-exit memcmp on peer-supplied MACs, leaking prefix matches. Any routable host can reach a listening SCTP endpoint without credentials, and a recovered MAC permits forged associations or authenticated chunks that can disclose data, redirect traffic, or hang the kernel.

CVSS severity8.1
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Timing discrepancy in Linux kernel SCTP allows remote attackers to recover authentication MACs through network timing measurements. The COOKIE ECHO path in sctp_unpack_cookie and AUTH path in sctp_sf_authenticate use early-exit memcmp on peer-supplied MACs, leaking prefix matches. Any routable host can reach a listening SCTP endpoint without credentials, and a recovered MAC permits forged associations or authenticated chunks that can disclose data, redirect traffic, or hang the kernel.

The record

CVE
CVE-2025-40204
Published
Nov 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0b32ff285ff6f6f1ac1d9495787ccce8837d6405
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0e8b8c326c2a6de4d837b1bb034ea704f4690d77
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1cd60e0d0fb8f0e62ec4499138afce6342dc9d4c
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8019b3699289fce3f10b63f98601db97b8d105b0
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9c05d44ec24126fc283835b68f82dba3ae985209
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b93fa8dc521d00d2d44bf034fb90e0d79b036617
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <dd91c79e4f58fbe2898dac84858033700e0e99fb
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ed3044b9c810c5c24eb2830053fbfe5fd134c5d4
  9. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0b32ff285ff6f6f1ac1d9495787ccce8837d6405; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0e8b8c326c2a6de4d837b1bb034ea704f4690d77; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1cd60e0d0fb8f0e62ec4499138afce6342dc9d4c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8019b3699289fce3f10b63f98601db97b8d105b0; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9c05d44ec24126fc283835b68f82dba3ae985209; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b93fa8dc521d00d2d44bf034fb90e0d79b036617; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <dd91c79e4f58fbe2898dac84858033700e0e99fb; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ed3044b9c810c5c24eb2830053fbfe5fd134c5d4; version=2.6.12

Published CVSS scores

5.3OracleCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
8.1Linux kernel CVE teamCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

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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