Bug 2554923 (CVE-2026-98591)

Summary:	CVE-2026-98591 kernel: bpf: Fix bounds check for skb-backed dynptrs
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) subsystem. An integer underflow in the bounds-checking logic for network packet buffer pointers allows validation checks to pass incorrectly. A local user capable of running BPF programs could exploit this flaw to create pointers referencing invalid memory, potentially leading to out-of-bounds memory access, a denial of service (system crash), or privilege escalation.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-18 15:32:57 UTC

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix bounds check for skb-backed dynptrs

The skb_pointer_if_linear() function checks whether a
memory region of length len starting at offset off into
the skb is in the linear area, and returns a pointer to
the region if so. The check currently subtracts between
skb_headlen and offset of the check, and since skb_headlen
is unsigned the subtraction can underflow. This causes the
bounds check to spuriously pass and generate an arbitrary
pointer of the form *(skb->data + off).

The only user of this helper is currently skb-backed BPF
dynptr code. Returning the wrong pointer leads to the
dynptr erroneously being backed with invalid memory.

Ensure the subtraction cannot underflow, and fail the check if
it would. Use u64 arithmetic to also prevent overflow when
calculating (skb_headlen(skb) - off) since off is unsigned.