Linux Kernel up to 4.13.5 fork fs/userfaultfd.c userfaultfd_ctx_put use after free

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A vulnerability was found in Linux Kernel up to 4.13.5 (Operating System). It has been classified as critical. This affects the function userfaultfd_ctx_put of the file fs/userfaultfd.c of the component fork Handler. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

A use-after-free flaw was found in fs/userfaultfd.c in the Linux kernel before 4.13.6. The issue is related to the handling of fork failure when dealing with event messages. Failure to fork correctly can lead to a situation where a fork event will be removed from an already freed list of events with userfaultfd_ctx_put().

The bug was discovered 10/03/2017. The weakness was published 01/14/2018 (Website). The advisory is shared at This vulnerability is uniquely identified as CVE-2017-15126 since 10/08/2017. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

The vulnerability was handled as a non-public zero-day exploit for at least 103 days. During that time the estimated underground price was around $5k-$25k. The vulnerability scanner Nessus provides a plugin with the ID 109380 (CentOS 7 : kernel (CESA-2018:1062)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family CentOS Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 236711 (Red Hat Update for kernel-rt (RHSA-2018:0676)).

Upgrading to version 4.13.6 eliminates this vulnerability. A possible mitigation has been published 4 months after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (109380).







CPE 2.3info

CPE 2.2info


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VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.7

VulDB Base Score: 5.6
VulDB Temp Score: 5.4
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NVD Base Score: 8.1
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Class: Use after free
CWE: CWE-416 / CWE-119

Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

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Nessus ID: 109380
Nessus Name: CentOS 7 : kernel (CESA-2018:1062)
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Threat Intelligenceinfo

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Recommended: Upgrade
Status: 🔍

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Upgrade: Kernel 4.13.6


10/03/2017 🔍
10/08/2017 +5 days 🔍
12/05/2017 +58 days 🔍
01/14/2018 +40 days 🔍
01/14/2018 +0 days 🔍
01/15/2018 +1 days 🔍
04/27/2018 +102 days 🔍
04/27/2018 +0 days 🔍
01/20/2023 +1729 days 🔍



Advisory: RHSA-2018:1062
Status: Not defined

CVE: CVE-2017-15126 (🔍)
SecurityFocus: 102516 - Linux Kernel 'fs/userfaultfd.c' Local Use After Free Memory Corruption Vulnerability


Created: 01/15/2018 11:20 AM
Updated: 01/20/2023 07:41 PM
Changes: 01/15/2018 11:20 AM (76), 12/23/2019 02:46 PM (4), 01/20/2023 07:34 PM (5), 01/20/2023 07:41 PM (1)
Complete: 🔍
Cache ID: 44:456:40


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