CVE-2015-8839
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Description
A flaw was found in the Linux kernel when attempting to "punch a hole" in files existing on an ext4 filesystem. When punching holes into a file races with the page fault of the same area, it is possible that freed blocks remain referenced from page cache pages mapped to process' address space.
Statement
This issue does not affect the Linux kernels as shipped with Red Hat Enterprise Linux 5 and 6.
This issue affects the Linux kernels as shipped with Red Hat Enterprise Linux 7 and MRG-2 kernels.
Additional information
- Bugzilla 1323577: kernel: ext4 filesystem page fault race condition with fallocate call.
- CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
- FAQ: Frequently asked questions about CVE-2015-8839
Common Vulnerability Scoring System (CVSS) Score Details
Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
| Red Hat | NVD | |
|---|---|---|
CVSS v2 Base Score | 4.7 | 1.9 |
Attack Vector | Local | Local |
Access Complexity | Medium | Medium |
Authentication | None | None |
Confidentiality Impact | None | None |
Integrity Impact | Complete | None |
Availability Impact | None | Partial |
CVSS v2 Vector
Red Hat: AV:L/AC:M/Au:N/C:N/I:C/A:N
NVD: AV:L/AC:M/Au:N/C:N/I:N/A:P
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When a race condition makes it possible to bypass a resource cleanup routine or trigger multiple initialization routines, it may lead to resource exhaustion.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Instability
When a race condition allows multiple control flows to access a resource simultaneously, it might lead the product(s) into unexpected states, possibly resulting in a crash.
Confidentiality,Integrity
Technical Impact: Read Files or Directories; Read Application Data
When a race condition is combined with predictable resource names and loose permissions, it may be possible for an attacker to overwrite or access confidential data (CWE-59).
Access Control
Technical Impact: Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Bypass Protection Mechanism
This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider.
Frequently Asked Questions
Why is Red Hat's CVSS v3 score or Impact different from other vendors?
My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
What can I do if my product is listed as "Will not fix"?
What can I do if my product is listed as "Fix deferred"?
What is a mitigation?
I have a Red Hat product but it is not in the above list, is it affected?
Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?
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