Bug 2535349 (CVE-2026-89882)

Summary:	CVE-2026-89882 kernel: media: rkvdec: hevc: guard INTER_REF_PIC_SET_PRED index underflow
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 RKVDEC HEVC decoder. A local attacker, by crafting a specific V4L2 control, could trigger an index underflow in the st_ref_pic_set_prediction() function. This underflow leads to an out-of-bounds read, potentially allowing for information disclosure or denial of service.	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 2026-09-16 12:13:47 UTC

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

media: rkvdec: hevc: guard INTER_REF_PIC_SET_PRED index underflow

st_ref_pic_set_prediction() computes the reference RPS index as
st_rps_idx - (delta_idx_minus1 + 1) per HEVC spec equation 7-59.
Both operands are u8, so when delta_idx_minus1 + 1 exceeds the
current index the subtraction wraps and the subsequent array access
at calculated_rps_st_sets[ref_rps_idx] reads far out of bounds.

A userspace V4L2 client that can open the RKVDEC m2m decoder can
submit an EXT_SPS_ST_RPS control with INTER_REF_PIC_SET_PRED set
and delta_idx_minus1 crafted to trigger the underflow.

Reject the entry early when the reference index would underflow.

Comment 1 Mauro Matteo Cascella 2026-09-22 15:41:40 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89882.mbox