How severe is CVE-2026-63993?

CVE-2026-63993 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-63993 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-63993?

CVE-2026-63993 primarily affects Linux Linux Kernel. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-63993?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-63993 published?

CVE-2026-63993 was published on 2026-07-19 and last updated on 2026-10-02.

CVE-2026-63993

CVE-2026-63993 is a critical-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-416
Affected product: Linux Linux Kernel
Published: 2026-07-19
Last modified: 2026-10-02

Description

In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.

Frequently asked questions

What is CVE-2026-63993?: In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.
How severe is CVE-2026-63993?: CVE-2026-63993 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-63993 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-63993?: CVE-2026-63993 primarily affects Linux Linux Kernel. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-63993?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-63993 published?: CVE-2026-63993 was published on 2026-07-19 and last updated on 2026-10-02.

References

Affected products (6)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:*

More vulnerabilities in Linux Linux Kernel

CVE-2026-63795 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error…
CVE-2025-38429 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: bus: mhi: ep: Update read pointer only after…
CVE-2025-22021 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: netfilter: socket: Lookup orig tuple for IPv6…
CVE-2025-21663 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: net: stmmac: dwmac-tegra: Read iommu stream id…
CVE-2024-56719 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix TSO DMA API usage causing…
CVE-2024-44984 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: bnxt_en: Fix double DMA unmapping for…

All CVEs affecting Linux Linux Kernel →

Other CWE-416 (Use After Free) vulnerabilities

CVE-2026-63795 — Critical (CVSS 10.0): In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error…
CVE-2026-13782 — Critical (CVSS 10.0): Use after free in Browser in Google Chrome prior to 150.0.7871.47 allowed a remote attacker who had compromised the…
CVE-2026-4725 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149…
CVE-2026-4688 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox…
CVE-2025-24085 — Critical (CVSS 10.0): A use after free issue was addressed with improved memory management. This issue is fixed in iOS 18.3 and iPadOS 18.3,…
CVE-2024-43102 — Critical (CVSS 10.0): Concurrent removals of certain anonymous shared memory mappings by using the UMTX_SHM_DESTROY sub-request of…

Browse all CWE-416 (Use After Free) vulnerabilities →