CVE-2026-53362: Linux Kernel Unspecified Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Linux Kernel. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-08-27, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-08-30; treat that as the outer limit, not the target.
• EPSS 0.7%, percentile 53: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 53% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
• Editorial verdict: Patch this week. Linux Kernel: Five Exploited Root Bugs Added to CISA KEV — Five local root bugs, all with fixes and most with public exploits, are now confirmed exploited; get every Linux host onto a current kernel and reboot this week, container hosts, CI runners and shared servers first.

What it is

In the Linux kernel, the following vulnerability has been resolved: ipv6: account for fraggap on the paged allocation path In ip6appenddata(), when the paged-allocation branch is taken (MSGMORE / NETIFFSG / large fraglen), alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap (datalen = length + fraggap). When fraggap is non-zero, this is not the first skb and transhdrlen is zero. The fraggap bytes carried over from the previous skb are copied just past the fragment headers in the new skb's linear area. The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount, and the copy writes past skb->end into the trailing skbsharedinfo. An unprivileged user can trigger this via a UDPv6 socket using MSGMORE together with MSGSPLICEPAGES. The bad accounting was introduced by commit 773ba4fe9104 ("ipv6: avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix ip6appenddata()'s handling of MSGSPLICEPAGES"), the negative copy value caused -EINVAL to be returned. That later commit allowed MSGSPLICEPAGES to proceed in this case, making the corruption triggerable. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic. Since a negative copy is no longer expected for a valid MSGSPLICEPAGES case, remove the MSGSPLICEPAGES exception from the negative copy check.

CISA’s summary

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.

Weakness type: CWE-122.

Product: Linux Kernel · Assigned by: Linux · Published: 2026-07-04

Affected and fixed versions

Severity scores

• Attack vector: local access needed
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2026-08-27; federal due date 2026-08-30. Known ransomware use: Unknown.
• CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.71% probability of exploitation activity in the next 30 days; percentile 53.

Timeline

• 2026-07-04 — CVE record published by Linux
• 2026-08-27 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-08-30 — CISA remediation deadline for US federal agencies
• 2026-09-18 — erroneo.us brief: Linux Kernel: Five Exploited Root Bugs Added to CISA KEV
• 2026-10-15 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
2. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
3. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
4. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
5. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
6. Listed in CISA KEV notes (git.kernel.org) git.kernel.org

Vulnerability records

1. CVE.org record CVE-2026-53362 cve.org
2. NVD entry CVE-2026-53362 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov
2. Listed in CISA KEV notes (cisa.gov) cisa.gov
3. Listed in CISA KEV notes (cisa.gov) cisa.gov

Other references from the CVE record and advisory

1. cert-portal.siemens.com cert-portal.siemens.com

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