Bug 2502415 (CVE-2026-63912)

Summary: CVE-2026-63912 kernel: xfrm: esp: restore combined single-frag length gate
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Encapsulating Security Payload (ESP) component. This vulnerability occurs in the ESP out-of-place fast path when handling combined single-fragment lengths. An attacker could potentially trigger a scenario where the system rejects the page-fragment fast path, leading to a denial of service (DoS) condition. This issue affects both IPv4 and IPv6.
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Description OSIDB Bzimport 2026-07-19 16:06:55 UTC 
In the Linux kernel, the following vulnerability has been resolved:

xfrm: esp: restore combined single-frag length gate

The ESP out-of-place fast path appends the trailer in esp_output_head()
before esp_output_tail() allocates the destination page frag. The
head-side gate currently checks skb->data_len and tailen separately, but
the tail code allocates a single destination frag from the combined
post-trailer skb->data_len.

Reject the page-frag fast path when the combined aligned length exceeds a
page. Otherwise skb_page_frag_refill() may fall back to a single page while
the destination sg still spans the combined skb->data_len.

Restore this combined-length page gate for both IPv4 and IPv6.
Comment 1 Keith Grant 2026-07-21 21:01:38 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071946-CVE-2026-63912-a43c@gregkh/T