New Linux Kernel Vulnerability Fragnesia Allows Root Privilege Escalation

Summary

A new Linux kernel vulnerability tracked as CVE-2026-46300, dubbed Fragnesia, resides in the XFRM ESP-in-TCP subsystem and allows unprivileged local attackers to escalate privileges to root by corrupting kernel memory and modifying system files like /usr/bin/su or /etc/passwd. Similar to previously disclosed Dirty Frag and Copy Fail vulnerabilities, Fragnesia affects a majority of Linux distributions, which have begun releasing patches. While a proof-of-concept exists, there is currently no evidence of active exploitation in the wild.

Full text

Linux distributions are informing users about a new kernel vulnerability that can be exploited by a local attacker to escalate privileges to root. Dubbed Fragnesia and officially tracked as CVE-2026-46300, the issue resides in the kernel’s XFRM ESP-in-TCP subsystem, allowing an unprivileged attacker to gain root permissions by overwriting sensitive system files. A majority of Linux distributions are affected, and they have started releasing patches. A proof-of-concept (PoC) exploit is available, but there is no evidence that Fragnesia has been exploited in the wild. “Similar to Dirty Frag, Fragnesia exploits a vulnerability in the XFRM ESP-in-TCP subsystem to achieve a memory write primitive in the kernel,” Microsoft’s threat intelligence team said. “The primitive is then used to corrupt the page cache memory of the [/]usr[/]bin[/]su binary, which in turn leads to launching a shell with root privilege. Note that exploitation is not constrained to use the [/]usr[/]bin[/]su binary; it can modify any file readable by the user, including [/]etc[/]passwd,” it added.Advertisement. Scroll to continue reading. Microsoft has urged organizations to apply the available patches as soon as possible. Fragnesia is in the same class of vulnerabilities as the recently disclosed Dirty Frag and Copy Fail. Copy Fail has been exploited in the wild, and Microsoft noted shortly after Dirty Frag’s disclosure that it too may have been leveraged in malicious attacks. The tech giant reported on May 8 that its Defender product had seen limited in-the-wild activity that could indicate exploitation of either Dirty Frag or Copy Fail. At the time of writing, there do not appear to be any other reports confirming the exploitation of Dirty Frag. Related: OpenSSH Flaw Allowing Full Root Shell Access Lurked for 15 Years Related: Easily Exploitable ‘Pack2TheRoot’ Linux Vulnerability Leads to Root Access Related: Organizations Warned of Exploited Linux Vulnerabilities Written By Eduard Kovacs Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. Daily Briefing Newsletter Subscribe to the SecurityWeek Email Briefing for the latest cybersecurity threats, trends, and expert insights. More from Eduard Kovacs Drupal Patches Highly Critical Vulnerability Exposing Websites to HackingGoogle’s Surge in Chrome Vulnerability Discoveries Likely Driven by AIAnthropic Silently Patches Claude Code Sandbox BypassReal-World ICS Security Tales From the TrenchesDrupal to Patch Highly Critical Vulnerability at Risk of Quick ExploitationMicrosoft Disrupts Malware-Signing Service Run by ‘Fox Tempest’ Critical Vulnerability Exposes Industrial Robot Fleets to HackingMillions Impacted Across Several US Healthcare Data Breaches Latest News Drupal Vulnerability in Hacker Crosshairs Shortly After DisclosureIn Other News: Industrial Router Exploitation, CISA KEV Nomination Form, Gas Station HackingCanadian Man Arrested for Operating Kimwolf Botnet‘First VPN’ Cybercrime Service Disrupted, Administrator ArrestedTrendAI Patches Apex One Zero-Day Exploited in the WildGrafana Says Codebase and Other Data Stolen via TanStack Supply Chain AttackCisco Patches Critical Vulnerability in Secure WorkloadOcean Emerges From Stealth With $28M for Agentic Email Security Platform Trending Daily Briefing NewsletterSubscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts. Virtual Event: Threat Detection and Incident Response Summit May 20, 2026 Delve into big-picture strategies to reduce attack surfaces, improve patch management, conduct post-incident forensics, and tools and tricks needed in a modern organization. Register Webinar: Third-Party Risk in Practice June 4, 2026 Organizations are investing heavily in third-party risk management, but breaches, delays, and blind spots continue to persist. Join this live webinar as we examine the gap between how organizations think their third-party risk programs are performing and what’s actually happening in practice. Register People on the MoveJoe Chen has become Chief Technology Officer at Trellix.Usercentrics has named Pawan Hegde as COO and Elena Ignatova as CPTO.SecureAuth has named Mark van Oppen as Chief Revenue Officer.More People On The MoveExpert Insights Caught Off Guard: Securing AI After It Hits Production As enterprises rush AI projects into production, security teams are increasingly being forced into reactive mode. (Joshua Goldfarb) Cyber Resilience is the New Business Continuity Plan The organizations best prepared to face disruption are those that align security, continuity and risk management around what the business cannot afford to lose. (Steve Durbin) Enhancing Data Center Security Without Sacrificing Performance For AI data centers, where the stakes are the highest and performance constraints are the tightest, security and performance are no longer a zero-sum game. (Nadir Izrael) Is the SOC Obsolete, and We Just Haven’t Admitted It Yet? Many AI-first enterprises have already embraced sovereign architectures for general AI initiatives; cybersecurity—and the SOC—should be next. (Danelle Au) The Mythos Moment: Enterprises Must Fight Agents with Agents Only with the right platform and an agentic, AI-driven defense, will enterprises be able to protect themselves in the agentic era. (Etay Maor) Flipboard Reddit Whatsapp Whatsapp Email

Indicators of Compromise

• cve — CVE-2026-46300

Entities