Security Experts:

Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Application Security

Privilege Escalation Bugs Patched in Linux Kernel

A total of five vulnerabilities that could lead to local privilege escalation were recently identified and fixed in the Linux kernel.

Identified by Positive Technologies security researcher Alexander Popov, the high severity bugs resided in the virtual socket implementation of the Linux kernel.

A total of five vulnerabilities that could lead to local privilege escalation were recently identified and fixed in the Linux kernel.

Identified by Positive Technologies security researcher Alexander Popov, the high severity bugs resided in the virtual socket implementation of the Linux kernel.

Tracked as CVE-2021-26708 and featuring a CVSS score of 7.0, the security holes were introduced in Linux kernel version 5.5 in November 2019.

The vulnerabilities are the result of race conditions that were added with virtual socket (VSOCK) multi-transport support, with all major GNU/Linux distributions impacted, as the vulnerable kernel drivers (CONFIG_VSOCKETS and CONFIG_VIRTIO_VSOCKETS) are shipped to all of them, as kernel modules.

Upon the creation of an AF_VSOCK socket, the vulnerable modules are automatically loaded, Positive Technologies explains. The bugs can be abused by unprivileged users.

The issues, Popov says, are race conditions rooted in wrong locking in net/vmw_vsock/af_vsock.c.

The bug exists because the vsock_sock.transport pointer is copied to a local variable that is used after lock_sock() is called. However, the vsock_sock.transport value may change before lock_sock() is called, thus causing the race condition.

The suggested fix involves copying the vsock_sock.transport pointer to the local value after lock_sock() has been called.

“I successfully developed a prototype exploit for local privilege escalation on Fedora 33 Server, bypassing x86_64 platform protections such as SMEP and SMAP. This research will lead to new ideas on how to improve Linux kernel security,” Popov commented.

In addition to identifying the vulnerabilities, the security researcher prepared a patch and sent it to the Linux kernel security team. The fix was merged into mainline kernel version 5.11-rc7 and also got backported into affected stable trees.

Related: BleedingTooth: Vulnerabilities in Linux Bluetooth Allow Zero-Click Attacks

Related: Patch Released for Linux Kernel Vulnerability Disclosed at Hacking Contest

Related: Serious Vulnerabilities in Linux Kernel Allow Remote DoS Attacks

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join this webinar to learn best practices that organizations can use to improve both their resilience to new threats and their response times to incidents.

Register

Join this live webinar as we explore the potential security threats that can arise when third parties are granted access to a sensitive data or systems.

Register

Expert Insights

Related Content

Application Security

Cycode, a startup that provides solutions for protecting software source code, emerged from stealth mode on Tuesday with $4.6 million in seed funding.

Vulnerabilities

Less than a week after announcing that it would suspended service indefinitely due to a conflict with an (at the time) unnamed security researcher...

Cybercrime

The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.

Data Breaches

LastPass DevOp engineer's home computer hacked and implanted with keylogging malware as part of a sustained cyberattack that exfiltrated corporate data from the cloud...

Application Security

PayPal is alerting roughly 35,000 individuals that their accounts have been targeted in a credential stuffing campaign.

Cybercrime

No one combatting cybercrime knows everything, but everyone in the battle has some intelligence to contribute to the larger knowledge base.

Application Security

GitHub this week announced the revocation of three certificates used for the GitHub Desktop and Atom applications.

Risk Management

The supply chain threat is directly linked to attack surface management, but the supply chain must be known and understood before it can be...