CVE-2026-53362: Linux Kernel Unspecified Vulnerability
Linux Kernel contains an unspecified vulnerability that can allow for privilege escalation via IPv6 networking subsystem. This vulnerability can impact multiple products, including but not limited to Suse, Red Hat, and other products using Linux.
Overview
A heap-based out-of-bounds write in the Linux kernel's IPv6 output path allows a local user with minimal privileges to corrupt kernel memory and escalate to root. The flaw sits in the paged-allocation branch of the UDPv6 send path and is reachable by any user who can open a socket. Kernels from version 6.0 through the fixed boundaries in the 6.1.x and 6.6.x stable lines are affected, as are downstream distributions such as SUSE and Red Hat that ship those kernel versions.
Vulnerability details
In the kernel function __ip6_append_data(), the paged-allocation branch, taken when MSG_MORE or scatter-gather is active, computes the new socket buffer's linear area size as fragheaderlen plus transhdrlen, omitting fraggap entirely. When a multi-fragment UDP send carries leftover bytes from the previous socket buffer, those bytes are copied into the undersized linear area, writing past skb->end into the trailing skb_shared_info structure. This is a classic heap-based buffer overflow: the allocation is too small for the data being written, and the overflow corrupts adjacent kernel heap metadata.
An attacker with a low-privilege local account sends data on a UDPv6 socket using both the MSG_MORE and MSG_SPLICE_PAGES flags, which forces the kernel down the paged-allocation path with a non-zero fraggap value. The resulting out-of-bounds write corrupts skb_shared_info, a well-understood target for kernel heap exploitation techniques. Successful exploitation yields full privilege escalation, giving the attacker root-level control of the host. No network access or interaction from another user is required beyond the ability to open a socket.
Severity and impact
Exploitation status
This vulnerability is confirmed as actively exploited in the wild — it is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.
Detection and monitoring
- Monitor for unexpected privilege changes on local user accounts: a process that transitions from an unprivileged UID to UID 0 without a corresponding sudo, su, or PAM authentication event in /var/log/auth.log or the audit log is a strong indicator of local privilege escalation.
- Audit syscall sequences combining sendmsg calls carrying MSG_MORE and MSG_SPLICE_PAGES flags on AF_INET6 SOCK_DGRAM sockets from non-root processes. Linux audit rules on the sendmsg syscall with filtering on socket family and flag values can surface this pattern without generating excessive noise on healthy systems.
Remediation
Additional hardening
- Update the Linux kernel to version 6.1.177 or later on the 6.1.x line, or 6.6.144 or later on the 6.6.x line. Downstream distributions such as SUSE and Red Hat should be updated to the vendor-supplied kernel packages that incorporate these fixes; see References for the upstream patch commits.
- Restrict local user access on systems where it is not operationally required. Reducing the number of accounts that can open sockets limits the population of users who can reach the vulnerable code path.
- Where kernel lockdown or seccomp profiles are deployed, ensure they restrict MSG_SPLICE_PAGES usage for untrusted processes. Confining application socket flag usage through seccomp-bpf policies raises the bar for triggering the paged-allocation path.
- Apply network segmentation to limit lateral movement in the event a host is compromised via local privilege escalation. Hosts running affected kernel versions that cannot be patched immediately should have their local user access audited and minimized.
Key dates
References
- https://git.kernel.org/stable/c/14200d435af9a9eeb444f529fc2f689a236b7962
- https://git.kernel.org/stable/c/46f201f8b4c39633a1fa3dc12459f506d470993d
- https://git.kernel.org/stable/c/6374fb9edf72c67a118a2c214a0dddd04c921e0a
- https://git.kernel.org/stable/c/65fb14cbebb0cd0eff903a22d33537ddc8b95769
- https://git.kernel.org/stable/c/736b380e28d0480c7bc3e022f1950f31fe53a7c5
- https://git.kernel.org/stable/c/e9eacf19281ea2498b36291b56c9606118c2d74e
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
Frequently asked questions
Does CVE-2026-53362 affect my FedRAMP authorization?
If Linux Kernel runs inside your authorization boundary, yes. CVE-2026-53362 appears on CISA's Known Exploited Vulnerabilities (KEV) catalog, with a remediation deadline of August 30, 2026. For a FedRAMP-authorized service, an unpatched KEV within the boundary is a finding. You must either remediate it or formally document a mitigation before your assessor or sponsoring agency raises it as a deficiency.
How does Knox help me handle CVE-2026-53362?
Knox does not patch Linux Kernel on your behalf. Under the FedRAMP shared-responsibility model, remediating CVE-2026-53362 is your obligation. What Knox provides is the pre-authorized, single-tenant boundary in which you carry out that remediation, plus continuous compliance monitoring and audit-artifact coverage to document the fix for your next assessment. The work is yours to execute; maintaining a compliant posture while you do it is not something you manage alone.
How does Knox's monitoring help with vulnerabilities like this?
Knox's automated continuous monitoring platform watches your environment for newly disclosed vulnerabilities and compliance issues on an ongoing basis. When something like CVE-2026-53362 surfaces, exposure appears during continuous monitoring rather than waiting to be flagged at an assessor review, giving you time to act before it becomes a formal finding.
How do I get FedRAMP authorized with Knox?
Knox runs a FedRAMP-as-a-Service platform. It gives SaaS vendors a pre-authorized cloud boundary on AWS, Azure, and GCP. Your application inherits 60-80% of the required security controls. You reach FedRAMP authorization in about 90 days for roughly 90% less than the traditional $3.5M path. Book a meeting and Knox will map your path to authorization.
What happens if CVE-2026-53362 isn't remediated by August 30, 2026?
Missing the August 30, 2026 deadline turns CVE-2026-53362 into a Plan of Action and Milestones (POA&M) item. A growing POA&M list is what converts a routine continuous-monitoring review into a difficult conversation with your sponsoring agency. Remediating on time keeps your authorization standing intact and the agency relationship straightforward.
Ready to achieve FedRAMP authorization in 90 days or less?
Schedule a meeting to discuss scope, parse readiness, and map your company’s accelerated path to FedRAMP authorization.
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