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CVE-2019-15791— Reference count underflow in shiftfs

Quick assessment

Affected
Ubuntu Shiftfs in the Linux kernel
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会发布的开源操作系统Linux所使用的内核。Canonical Ubuntu Linux是英国Canonical公司的一套Linux操作系统。 Canonical Ubuntu Linux 18.04（lts）版本和19.04版本中的Linux kernel 5.0版本和5.3版本的shiftfs实现存在数字错误漏洞。本地攻击者可利用该漏洞造成拒绝服务（系统崩溃）或可能执行任意代码。

CVSS 7.1 · High EPSS 1.32% · P70

Public Exploits 1

ExploitDB · 1 EDB-47693#CVE-2019-15791 [dos]

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth
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I. Basic Information for CVE-2019-15791

Vulnerability Information
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Vulnerability Title
Reference count underflow in shiftfs
Source: CVE Program / CVE List V5
Vulnerability Description
In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() installs an fd referencing a file from the lower filesystem without taking an additional reference to that file. After the btrfs ioctl completes this fd is closed, which then puts a reference to that file, leading to a refcount underflow.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
在过期或释放后对资源进行操作
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 数字错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会发布的开源操作系统Linux所使用的内核。Canonical Ubuntu Linux是英国Canonical公司的一套Linux操作系统。 Canonical Ubuntu Linux 18.04（lts）版本和19.04版本中的Linux kernel 5.0版本和5.3版本的shiftfs实现存在数字错误漏洞。本地攻击者可利用该漏洞造成拒绝服务（系统崩溃）或可能执行任意代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Ubuntu Shiftfs in the Linux kernel 5.3.0-11.12 ~ 5.3 kernel* -

II. Public POCs for CVE-2019-15791

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III. Intelligence Information for CVE-2019-15791

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Vendor Advisories for CVE-2019-15791 (2)

Other References for CVE-2019-15791 (1)

Same Patch Batch · Ubuntu · 2020-04-23 · 4 CVEs total

CVE-2019-15792 7.1 HIGH Type confusion in shiftfs
CVE-2019-15794 7.1 HIGH Reference counting error in overlayfs/shiftfs error path when used in conjuction with aufs
CVE-2019-15793 6.5 MEDIUM Mishandling of file-system uid/gid with namespaces in shiftfs

IV. Related Vulnerabilities

Same product: Shiftfs in the Linux kernel
Same vendor: Ubuntu
Same weakness: CWE-672

V. Comments for CVE-2019-15791

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