CVE-2026-63971

Local denial of service via SCTP wrong-lock race

Published Jul 19, 2026 · Updated Jul 19, 2026

Race condition in the Linux kernel SCTP implementation allows local users to cause system instability through concurrent socket operations. The sctp_wait_for_connect() path reacquires the original socket lock but accepts success after SCTP_SOCKOPT_PEELOFF migrates the association, so sctp_datamsg_from_user() continues under the wrong lock. Exploitation requires a local low-privileged user to race a connecting SCTP association against peeloff, resulting in incorrect memory access and denial of service.

CVSS severity7.8
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in the Linux kernel SCTP implementation allows local users to cause system instability through concurrent socket operations. The sctp_wait_for_connect() path reacquires the original socket lock but accepts success after SCTP_SOCKOPT_PEELOFF migrates the association, so sctp_datamsg_from_user() continues under the wrong lock. Exploitation requires a local low-privileged user to race a connecting SCTP association against peeloff, resulting in incorrect memory access and denial of service.

The record

CVE
CVE-2026-63971
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-367, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 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=4.16
  2. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d
  3. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <6140cfa721451fa6e18e134e709703c2bf34d0fb
  4. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <634a9af8a26a84d8b0d7b3b643204b344b42d9fb
  5. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <68667ee4c7dadf7f63167234e2a1af09b3f7874e
  6. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <7d2038d4b80166f7bead8d07eba3b97405816c21
  7. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <8e9b56051d24540cfbf39194618708c4a7633549
  8. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <bcfeac79af740735ace44008b4a11b8e5add20f5
  9. Affected versionversion=668c9beb9020d5834ee9e43c208190a07d2b1928 <f14fe6395a8b3d961a61e138ad7b36ba3626dd4e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=4.16; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <6140cfa721451fa6e18e134e709703c2bf34d0fb; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <634a9af8a26a84d8b0d7b3b643204b344b42d9fb; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <68667ee4c7dadf7f63167234e2a1af09b3f7874e; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <7d2038d4b80166f7bead8d07eba3b97405816c21; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <8e9b56051d24540cfbf39194618708c4a7633549; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <bcfeac79af740735ace44008b4a11b8e5add20f5; version=668c9beb9020d5834ee9e43c208190a07d2b1928 <f14fe6395a8b3d961a61e138ad7b36ba3626dd4e

Published CVSS scores

7.8Linux CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Red HatCVSS:3.1/AV:L/AC:H/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

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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