CVE-2025-21976 [Medium] | Security Vulnerability in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: fbdev: hyperv_fb: Allow graceful removal of framebuffer When a Hyper-V framebuffer device is unbind, hyperv_fb driver tries to release the framebuffer forcefully. If this framebuffer is in use it produce the following WARN and hence this framebuffer is never released. [ 44.111220] WARNING: CPU: 35 PID: 1882 at drivers/video/fbdev/core/fb_info.c:70 framebuffer_release+0x2c/0x40 < snip > [ 44.111289] Call Trace: [ 44.111290] <TASK> [ 44.111291] ? show_regs+0x6c/0x80 [ 44.111295] ? __warn+0x8d/0x150 [ 44.111298] ? framebuffer_release+0x2c/0x40 [ 44.111300] ? report_bug+0x182/0x1b0 [ 44.111303] ? handle_bug+0x6e/0xb0 [ 44.111306] ? exc_invalid_op+0x18/0x80 [ 44.111308] ? asm_exc_invalid_op+0x1b/0x20 [ 44.111311] ? framebuffer_release+0x2c/0x40 [ 44.111313] ? hvfb_remove+0x86/0xa0 [hyperv_fb] [ 44.111315] vmbus_remove+0x24/0x40 [hv_vmbus] [ 44.111323] device_remove+0x40/0x80 [ 44.111325] device_release_driver_internal+0x20b/0x270 [ 44.111327] ? bus_find_device+0xb3/0xf0 Fix this by moving the release of framebuffer and assosiated memory to fb_ops.fb_destroy function, so that framebuffer framework handles it gracefully. While we fix this, also replace manual registrations/unregistration of framebuffer with devm_register_framebuffer.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-04-02	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-04-02

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2025-21976

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2025-21976 not yet assigned priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2.	https://security-tracker.debian.org/tracker/CVE-2025-21976
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2025-21976
`suse`	medium	CVE-2025-21976 severity moderate: SUSE including 302 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 517 product×package rows across 56 product lines (Image SLES12-SP5-Azure-BYOS, Image SLES12-SP5-Azure-HPC-BYOS, … (56 product lines)): Known Affected 231, Known Not Affected 180, Fixed 106.	https://www.suse.com/security/cve/CVE-2025-21976/
`ubuntu`	medium	CVE-2025-21976 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, ignored 169, released 123, needed 74, not-affected 40.	https://ubuntu.com/security/CVE-2025-21976

Affected software / configurations for CVE-2025-21976

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 3.10, < 6.12.20	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.13.8	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc1::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc2::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc3::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc4::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc5::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc6::::::

References for CVE-2025-21976

URL	Tags
https://git.kernel.org/stable/c/4545e2aa121aea304d33903099c03e29ed4fe50a	Patch
https://git.kernel.org/stable/c/a7b583dc99c6cf4a96877017be1d08247e1ef2c7	Patch
https://git.kernel.org/stable/c/ea2f45ab0e53b255f72c85ccd99e2b394fc5fceb	Patch

URL

CVE-2025-21976 | fbdev: hyperv_fb: Allow graceful removal of framebuffer

Exploit prediction scoring system (EPSS) score for CVE-2025-21976

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21976

Weakness enumeration for CVE-2025-21976

OS Trackers for CVE-2025-21976

Affected software / configurations for CVE-2025-21976

References for CVE-2025-21976