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Linux bitten by second severe vulnerability in as many weeks
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Both privilege escalation vulnerabilities stem from bugs in the kernel’s handling of page caches stored in memory, allowing untrusted users to modify them. They target caches in networking and memory-fragment handling components. Specifically, CVE-2026-43284 attacks the esp4 and esp6 () processes, and CVE-2026-43500 zeroes in on rxrpc. Last week’s CopyFail exploited faulty page caching in the authencesn AEAD template process, which is used for IPsec extended sequence numbers. A 2022 vulnerability named Dirty Pipe also stemmed from flaws that allow attackers to overwrite page caches. Researchers from security firm Automox wrote: Dirty Frag belongs to the same bug family as Dirty Pipe and Copy Fail, but it targets the frag member of the kernel’s struct sk_buff rather than pipe_buffer. The exploit uses splice() to plant a reference to a read-only page-cache page (for example, /etc/passwd or /usr/bin/su) into the frag slot of a sender-side skb. Receiver-side kernel code then performs in-place cryptographic operations on that frag, modifying the page cache in RAM. Every subsequent read of the file sees the corrupted version, even though the attacker only ever had read access. CVE-2026-43284 is found in the esp_input() process on the IPsec ESP receive path. When an skb object is non-linear but lacks a frag list, the code skips skb_cow_data() and decrypts AEAD in place on the planted frag. From there, an attacker can control the file offset and the 4-byte value of each store. CVE-2026-43500, meanwhile, resides in rxkad_verify_packet_1(). The process decrypts RxRPC payloads using a single-block process. Splice-pinned pages become both a source and destination. That, paired with the decryption key being freely extracted using the add_key (rxrpc), allows an attacker to rewrite contents in memory. Either exploit used separately is unreliable. Some Ubuntu configurations use AppArmor to prevent untrusted users from creating namespace contents. That, in turn, neutralizes the ESP technique. Most other distributions by default don’t run rxrpc.ko, which neutralizes the RxRPC arm. When chained together, however, the two exploits allow attackers to obtain root on every major distribution Kim tested. Once the exploits run, attackers can use SSH access, web-shell execution, container escapes, or compromise low-privilege accounts. “Dirty Frag is notable because it introduces multiple kernel attack paths involving rxrpc and esp/xfrm networking components to improve exploitation reliability,” Microsoft researchers wrote. “Rather than relying on narrow timing windows or unstable corruption conditions often associated with Linux local privilege escalation exploits, Dirty Frag appears designed to increase consistency across vulnerable environments.” Researchers at Google-owned Wiz said exploits will be less likely to break out of hardened containerized environments such as Kubernets with default security settings in place. “However, the risk remains significant for virtual machines or less restricted environments.” The best response for anyone using Linux is to install patches immediately. While fixes likely require a reboot, protection from a threat as severe as Dirty Frag outweighs the cost of disruptions. Anyone who can’t install immediately should follow the mitigation steps laid out in the posts linked above. Additional guidance can be found here.
A severe security vulnerability affecting almost every version of the Linux operating system has caught defenders off-guard and scrambling to patch after security researchers publicly released exploit code that allows attackers to take complete control of vulnerable systems. The U.S. government says the bug, dubbed “CopyFail,” is now being exploited in the wild, meaning it’s being actively used in malicious hacking campaigns. The bug, officially tracked as CVE-2026-31431 and discovered in Linux kernel versions 7.0 and earlier, was disclosed to the Linux kernel security team in late March, and patched after about a week. But the patches have yet to fully trickle down to the many Linux distributions that rely on the vulnerable kernel, leaving any system running an affected Linux version at risk of compromise. Linux is widely used in enterprise settings, running the computers that operate much of the world’s datacenters. The CopyFail website says that the same short Python script “roots every Linux distribution shipped since 2017.” According to security firm Theori, which discovered CopyFail, the vulnerability was verified in several widely used versions of Linux including Red Hat Enterprise Linux 10.1, Ubuntu 24.04 (LTS), Amazon Linux 2023, as well as SUSE 16. Devops engineer and developer Jorijn Schrijvershof wrote in a blog post that the exploit works on Debian and Fedora versions, as well as Kubernetes, which relies on the Linux kernel. Schrijvershof described the bug as having an “unusually big blast radius” as it works on “nearly every modern distribution” of Linux. The bug is called CopyFail because the affected component in the Linux kernel, the core of the operating system that has virtually complete access to the entire device, does not copy certain data when it should. This corrupts sensitive data within the kernel, allowing the attacker to piggyback the kernel’s access to the rest of the system, including its data. If exploited, the bug is particularly problematic because it allows a regular, limited-access user to gain full-administrator access on an affected Linux system. A successful compromise of a server in a datacenter could allow an attacker to gain access to every application, server, and database of numerous corporate customers, and potentially gain access to other systems on the same network or datacenter. The CopyFail bug cannot be exploited over the internet on its own, but can be weaponized if used in conjunction with an exploit that works over the internet. Per Microsoft, if the CopyFail bug is chained together with another vulnerability that can be delivered over the internet, an attacker could use the flaw to gain root access to an affected server. A user operating a Linux computer with a vulnerable kernel could also be tricked into opening a malicious link or attachment that triggers the vulnerability. The bug could also be injected by way of supply chain attacks, in which malicious actors hack into an open source developer’s account and plant the malware in their code in order to compromise a large number of devices in one go. Given the risk to the federal enterprise network, U.S. cybersecurity agency CISA has ordered all civilian federal agencies to patch any affected systems by May 15. When you purchase through links in our articles, we may earn a small commission. This doesn’t affect our editorial independence. Zack Whittaker is the security editor at TechCrunch. He also authors the weekly cybersecurity newsletter, this week in security. He can be reached via encrypted message at zackwhittaker.1337 on Signal. You can also contact him by email, or to verify outreach, at zack.whittaker@techcrunch.com. View Bio
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