CVE-2017-1000253

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Last Modified: UTC

Important Important Impact What does this mean?
7.8 CVSS v3 Base Score

Description

A flaw was found in the way the Linux kernel loaded ELF executables. Provided that an application was built as Position Independent Executable (PIE), the loader could allow part of that application's data segment to map over the memory area reserved for its stack, potentially resulting in memory corruption. An unprivileged local user with access to SUID (or otherwise privileged) PIE binary could use this flaw to escalate their privileges on the system.

Statement

This issue affects the Linux kernel packages as shipped with Red Hat Enterprise Linux 5 and 6. This issue affects the Linux kernel packages as shipped with Red Hat Enterprise Linux 7 prior to kernel version 3.10.0-693, that is Red Hat Enterprise Linux 7.4 GA kernel version. Kernel versions after 3.10.0-693 contain the fix and are thus not vulnerable.

This issue affects the Linux kernel-rt packages prior to the kernel version 3.10.0-693.rt56.617 (Red Hat Enteprise Linux for Realtime) and 3.10.0-693.2.1.rt56.585.el6rt (Red Hat Enterprise MRG 2). The latest Linux kernel-rt packages as shipped with Red Hat Enterprise Linux for Realtime and Red Hat Enterprise MRG 2 are not vulnerable.

Future Linux kernel updates for the respective releases will address this issue.

Mitigation

By setting vm.legacy_va_layout to 1 we can effectively disable the exploitation of this issue by switching to the legacy mmap layout. The mmap allocations start much lower in the process address space and follow the bottom-up allocation model. As such, the initial PIE executable mapping is far from the reserved stack area and cannot interfere with the stack.

64-bit processes on Red Hat Enterprise Linux 5 are forced to use the legacy virtual address space layout regardless of the vm.legacy_va_layout value.

Note: Applications that have demands for a large linear address space (such as certain databases) may be unable to handle the legacy memory layout proposed using this mitigation. We recommend to test your systems and applications before deploying this mitigation on production systems.

Edit the /etc/sysctl.conf file as root, and add or amend:

    vm.legacy_va_layout = 1

To apply this setting, run the /sbin/sysctl -p command as the root user to reload the settings from /etc/sysctl.conf.

Verify that vm.legacy_va_layout is now set to defined value:

    $ /sbin/sysctl vm.legacy_va_layout
    vm.legacy_va_layout = 1

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2017-1000253

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2017-1000253

Content from www.qualys.com is not included.https://www.qualys.com/2017/09/26/cve-2017-1000253/cve-2017-1000253.txt

Content from www.cisa.gov is not included.https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 5 Extended Lifecycle Support kernel Fixed RHSA-2017:2801
Red Hat Enterprise Linux 5.9 Long Life kernel Fixed RHSA-2017:2802
Red Hat Enterprise Linux 6 kernel Fixed RHSA-2017:2795
Red Hat Enterprise Linux 6.2 Advanced Update Support kernel Fixed RHSA-2017:2800
Red Hat Enterprise Linux 6.4 Advanced Update Support kernel Fixed RHSA-2017:2799
Red Hat Enterprise Linux 6.5 Advanced Update Support kernel Fixed RHSA-2017:2798
Red Hat Enterprise Linux 6.5 Telco Extended Update Support kernel Fixed RHSA-2017:2798
Red Hat Enterprise Linux 6.6 Advanced Update Support kernel Fixed RHSA-2017:2797
Red Hat Enterprise Linux 6.6 Telco Extended Update Support kernel Fixed RHSA-2017:2797
Red Hat Enterprise Linux 6.7 Extended Update Support kernel Fixed RHSA-2017:2796
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

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 Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 7.8 7.8
Attack Vector Local Local
Attack Complexity Low Low
Privileges Required Low Low
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact High High
Integrity Impact High High
Availability Impact High High

CVSS v3 Vector

Red Hat CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Acknowledgements

Red Hat would like to thank Qualys Research Labs for reporting this issue.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.