CVE-2017-1000253
Linux Kernel PIE Stack Buffer Corruption Vulnerability
Description
CVE-2017-1000253 is a high-severity Linux kernel vulnerability affecting the ELF binary loader that allows a local authenticated attacker to escalate privileges to root. The flaw resides in the kernel's handling of position-independent executables (PIE) and was originally patched in upstream kernels in April 2015, but was not recognized as a security threat until September 2017 when Qualys researchers published their analysis. Affected systems include CentOS 6/7, Red Hat Enterprise Linux 6/7, and numerous Linux kernel versions prior to backported fixes. With an EPSS score of 54.2% (98.0th percentile) and a confirmed association with ransomware campaigns, CISA has added this vulnerability to its KEV catalog with a remediation deadline of September 30, 2024.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| centos | centos | 6.0; 6.1; 6.2; 6.3; 6.4; 6.5; 6.6; 6.7; 6.8; 6.9; 7.1406; 7.1503; 7.1511; 7.1611 |
| redhat | enterprise linux | 6.0; 6.1; 6.2; 6.3; 6.4; 6.5; 6.6; 6.7; 6.8; 6.9; 7.0; 7.1; 7.2; 7.3 |
| linux | linux kernel | >= 2.6.25, < 3.2.70; >= 3.3, < 3.4.109; >= 3.5, < 3.10.77; >= 3.11, < 3.12.43; >= 3.13, < 3.14.41; >= 3.15, < 3.16.35; >= 3.17, < 3.18.14; >= 3.19, < 3.19.7; >= 4.0, < 4.0.2 |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
- http://www.securityfocus.com/bid/101010(Third Party Advisory, VDB Entry)
- http://www.securitytracker.com/id/1039434(Third Party Advisory, VDB Entry)
- https://access.redhat.com/errata/RHSA-2017:2793(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2794(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2795(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2796(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2797(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2798(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2799(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2800(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2801(Third Party Advisory)
- https://access.redhat.com/errata/RHSA-2017:2802(Third Party Advisory)
- https://www.qualys.com/2017/09/26/cve-2017-1000253/cve-2017-1000253.txt(Patch, Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-1000253(US Government Resource)
Weakness Type
Stack-Based Buffer Overflow in ELF Loader
Although no formal CWE has been assigned to CVE-2017-1000253, the vulnerability is a stack-based buffer overflow in the Linux kernel's ELF binary loader. When the kernel loads a position-independent executable (PIE), it may fail to properly allocate sufficient stack space, allowing the executable's data segment to overlap with the stack region. This memory corruption primitive enables an attacker to overwrite stack data and achieve arbitrary code execution in kernel context. Stack-based buffer overflows in kernel code are especially dangerous because they run at the highest privilege level, providing immediate root access upon successful exploitation.
Learn more: CWE-121: Stack-based Buffer Overflow
Impact Analysis
The CVSS v3.1 base score of 7.8 (High) reflects a local privilege escalation vulnerability with complete system compromise potential. Confidentiality (C:H), integrity (I:H), and availability (A:H) are all fully compromised, granting the attacker root-level access that allows reading any file, modifying system configurations, installing persistent backdoors, and crashing or shutting down the system. The attack requires only local access with low privileges and no user interaction, making it exploitable by any user with shell access.
From a business perspective, this vulnerability is particularly concerning for shared hosting environments, containerized deployments, and multi-tenant systems where users have limited shell access. A successful exploit grants full root control, enabling the attacker to break out of user-level isolation and access other tenants' data. The EPSS score of 54.2% at the 98.0th percentile indicates extremely high exploitation activity — more than half of similarly scored vulnerabilities are actively exploited. This vulnerability has a confirmed "Known" ransomware association, meaning ransomware operators target unpatched Linux systems using this kernel flaw. The widespread deployment of affected CentOS and RHEL versions in enterprise server environments amplifies the business risk.
Exploit Maturity
CVE-2017-1000253 has a long history of active exploitation, with CISA adding it to the Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of September 30, 2024 — more than seven years after the vulnerability was publicly disclosed. The "Known" ransomware association in the KEV catalog confirms that ransomware groups actively target this vulnerability. The EPSS probability of 54.2% at the 98.0th percentile places this among the most heavily exploited kernel vulnerabilities tracked.
Qualys published a detailed technical analysis and proof of concept demonstrating reliable exploitation on CentOS 7 systems. The vulnerability's original kernel fix (commit a87938b2e246) was applied upstream in April 2015 but was not backported to long-term support distributions until Qualys identified the security impact in September 2017. Red Hat issued multiple emergency advisories (RHSA-2017:2793 through RHSA-2017:2802) covering RHEL 6 and 7 variants. Despite patches being available since 2017, the vulnerability continues to appear in the KEV catalog due to persistent exploitation of unpatched systems, particularly legacy CentOS 6 installations that have reached end-of-life.
Remediation
- Update the Linux kernel immediately — Apply the latest kernel packages for your distribution. For RHEL/CentOS 7, install the kernel updates referenced in Red Hat advisories RHSA-2017:2793 through RHSA-2017:2802. For upstream kernels, ensure you are running version 3.10.77 or later (for the 3.10.x branch) or any kernel that includes commit a87938b2e246.
- Migrate off end-of-life distributions — CentOS 6 reached end-of-life in November 2020 and no longer receives security updates. Systems still running CentOS 6 should be migrated to a supported distribution such as RHEL 8/9, Rocky Linux, or AlmaLinux to receive ongoing security patches.
- Restrict local shell access — Minimize the number of users with interactive shell access to Linux servers. Use SSH key-based authentication, disable password login, and implement jump-host architectures to reduce the attack surface for local privilege escalation.
- Deploy kernel live patching — For systems where reboot windows are limited, use kernel live patching solutions such as Red Hat kpatch, Canonical Livepatch, or KernelCare to apply security fixes without requiring a system restart.
- Implement mandatory access controls — Enable and properly configure SELinux (on RHEL/CentOS) or AppArmor (on Ubuntu/SUSE) to contain the impact of privilege escalation. Even if an attacker achieves root through this exploit, properly configured MAC policies can limit what actions the compromised process can perform.
Technical Details
The CVSS v3.1 vector for CVE-2017-1000253 is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, yielding a base score of 7.8 (High). Attack Vector (AV:L) requires local access to the target system. Attack Complexity (AC:L) indicates reliable exploitation without special conditions. Privileges Required (PR:L) means any authenticated user account suffices. User Interaction (UI:N) confirms no victim action is needed. Scope (S:U) is technically limited to the vulnerable component, though kernel compromise effectively compromises the entire system. Confidentiality (C:H), Integrity (I:H), and Availability (A:H) reflect complete system control via root access.
The vulnerability lies in the Linux kernel's load_elf_binary() function, specifically in how it handles position-independent executables (PIE) compiled with CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE enabled. When loading a PIE binary, the kernel allocates the executable's load address and stack in the virtual address space. Due to insufficient boundary checking, the data segment of the loaded binary can extend into the memory region allocated for the stack, creating a stack-to-data overlap condition. An attacker can craft a PIE executable with a specially sized data segment that causes this overlap, enabling controlled corruption of stack memory. By carefully manipulating the overlapping data, the attacker can overwrite the return address or other control flow data on the stack, redirecting execution to attacker-controlled code that runs in kernel context. Qualys demonstrated successful exploitation against default CentOS 7 installations, achieving reliable root access from an unprivileged user session.
Frequently Asked Questions
What is CVE-2017-1000253?
CVE-2017-1000253 is a Linux kernel privilege escalation vulnerability in the ELF binary loader that allows a local attacker with a low-privilege account to gain root access. The flaw involves a stack buffer overflow triggered by loading specially crafted position-independent executables (PIE), causing the binary's data segment to overlap with the kernel stack.
Why is a 2017 vulnerability still in CISA's KEV catalog?
Despite patches being available since 2017, many Linux systems — particularly those running end-of-life distributions like CentOS 6 — remain unpatched. CISA added this vulnerability to the KEV catalog because it continues to be actively exploited by threat actors, including ransomware operators, who specifically target legacy Linux servers that have not been updated.
Which Linux distributions are affected?
The primary affected distributions are CentOS 6.x and 7.x, Red Hat Enterprise Linux 6.x and 7.x, and upstream Linux kernels across multiple version branches (2.6.25 through 4.0.2 without the fix). Any Linux distribution that did not backport commit a87938b2e246 to its kernel is potentially vulnerable.
Is CVE-2017-1000253 associated with ransomware?
Yes. CISA's KEV catalog classifies this vulnerability with a "Known" ransomware association, confirming that ransomware groups actively exploit unpatched Linux systems using this kernel flaw. Organizations running vulnerable kernel versions should prioritize patching or migration to supported distributions immediately.
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