CVE-2026-63809

System crash via mismatched sysctl buffer free

Published Jul 19, 2026 · Updated Jul 19, 2026

Invalid pointer release in the Linux kernel BPF sysctl path allows local users to crash affected systems through a crafted sysctl write. proc_sys_call_handler() allocates a buffer with kvzalloc(), but the cgroup BPF replacement path releases it with kfree() even when allocation falls back to vmalloc(). Exploitation requires low-privileged local access, a cgroup BPF sysctl filter that replaces the buffer, and a sufficiently large allocation; the demonstrated result is a kernel Oops and system crash.

CVSS severity7.8
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Invalid pointer release in the Linux kernel BPF sysctl path allows local users to crash affected systems through a crafted sysctl write. proc_sys_call_handler() allocates a buffer with kvzalloc(), but the cgroup BPF replacement path releases it with kfree() even when allocation falls back to vmalloc(). Exploitation requires low-privileged local access, a cgroup BPF sysctl filter that replaces the buffer, and a sufficiently large allocation; the demonstrated result is a kernel Oops and system crash.

The record

CVE
CVE-2026-63809
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-763, 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=4508943794efdd94171549c0bd52810e2f4ad9fe <4c21b5927d4364bfe7365f2700da5fea0ed0d004
  2. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <65bd0c0afb0e1bf3287458e342429b069624f7d4
  3. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <70df4de46577fab5e25418f014583155a147c902
  4. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2
  5. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <81fc9a13acae99966232f0e055eb2e445263b89a
  6. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <838fe9c28121777c59a9406710a68fcf77bb8017
  7. Affected versionversion=4508943794efdd94171549c0bd52810e2f4ad9fe <e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2
  8. Affected versionversion=5.10.20 <5.10.260
  9. Affected versionversion=5.11.3 <5.12
  10. Affected versionversion=5.12
  11. Affected versionversion=66258ab303588936ee1ee0794d9a271be24f73cb
  12. Affected versionversion=b7925acd82926ebbf94a0f0783a3961f4e558856 <d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=4508943794efdd94171549c0bd52810e2f4ad9fe <4c21b5927d4364bfe7365f2700da5fea0ed0d004; version=4508943794efdd94171549c0bd52810e2f4ad9fe <65bd0c0afb0e1bf3287458e342429b069624f7d4; version=4508943794efdd94171549c0bd52810e2f4ad9fe <70df4de46577fab5e25418f014583155a147c902; version=4508943794efdd94171549c0bd52810e2f4ad9fe <77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2; version=4508943794efdd94171549c0bd52810e2f4ad9fe <81fc9a13acae99966232f0e055eb2e445263b89a; version=4508943794efdd94171549c0bd52810e2f4ad9fe <838fe9c28121777c59a9406710a68fcf77bb8017; version=4508943794efdd94171549c0bd52810e2f4ad9fe <e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2; version=5.10.20 <5.10.260; version=5.11.3 <5.12; version=5.12; version=66258ab303588936ee1ee0794d9a271be24f73cb; version=b7925acd82926ebbf94a0f0783a3961f4e558856 <d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e

Published CVSS scores

7.8Linux kernel 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-763Release of Invalid Pointer or Reference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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