CVE-2025-39698 [Medium] | Use-After-Free in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: io_uring/futex: ensure io_futex_wait() cleans up properly on failure The io_futex_data is allocated upfront and assigned to the io_kiocb async_data field, but the request isn't marked with REQ_F_ASYNC_DATA at that point. Those two should always go together, as the flag tells io_uring whether the field is valid or not. Additionally, on failure cleanup, the futex handler frees the data but does not clear ->async_data. Clear the data and the flag in the error path as well. Thanks to Trend Micro Zero Day Initiative and particularly ReDress for reporting this.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-09-06	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-09-06

—

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]
8.8	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.0	6.0	134c704f-9b21-4f2e-91b3-4a467353bcc0

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]

8.8

3.1

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.0

6.0

134c704f-9b21-4f2e-91b3-4a467353bcc0

OS Trackers for CVE-2025-39698

vendor	priority	summary	link
`debian`	unimportant	CVE-2025-39698 unimportant priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2025-39698
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2025-39698
`suse`	high	CVE-2025-39698 severity important: SUSE including 144 source package names (cluster-md-kmp-64kb-6.12.0-160000.6.1, cluster-md-kmp-default, …), 608 product×package rows across 126 product lines (Image SL-Micro, Image SL-Micro-Azure, … (126 product lines)): Known Not Affected 301, Fixed 285, First Fixed 22.	https://www.suse.com/security/cve/CVE-2025-39698/
`ubuntu`	high	CVE-2025-39698 high priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1414 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 1017, ignored 176, released 118, not-affected 95, needed 5, needs-triage 2, pending 1.	https://ubuntu.com/security/CVE-2025-39698

Affected software / configurations for CVE-2025-39698

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 6.7, < 6.12.44	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.16.4	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc1::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc2::::::

References for CVE-2025-39698

URL	Tags
https://git.kernel.org/stable/c/508c1314b342b78591f51c4b5dadee31a88335df	Patch
https://git.kernel.org/stable/c/d34c04152df517c59979b4bf2a47f491e06d3256	Patch
https://git.kernel.org/stable/c/d9f93172820a53ab42c4b0e5e65291f4f9d00ad2	Patch
https://www.zerodayinitiative.com/advisories/ZDI-25-915/	Third Party Advisory

URL

CVE-2025-39698 | io_uring/futex: ensure io_futex_wait() cleans up properly on failure

Exploit prediction scoring system (EPSS) score for CVE-2025-39698

Common vulnerability scoring system (CVSS) metrics for CVE-2025-39698

Weakness enumeration for CVE-2025-39698

OS Trackers for CVE-2025-39698

Affected software / configurations for CVE-2025-39698

References for CVE-2025-39698