Local privilege escalation via clipped-width count mismatch
Published Dec 8, 2025 · Updated Aug 5, 2026
An out-of-bounds write in Linux fbdev allows local users to escalate privileges through crafted framebuffer and console operations. In bit_putcs, clipping image width reduces the buffer allocation but leaves cnt at the original character count, so aligned and unaligned renderers write past the vmalloc buffer. Reachability requires access to a framebuffer character device or virtual console; the corruption can disclose or alter kernel memory or panic the system.
Summary
What happened
An out-of-bounds write in Linux fbdev allows local users to escalate privileges through crafted framebuffer and console operations. In bit_putcs, clipping image width reduces the buffer allocation but leaves cnt at the original character count, so aligned and unaligned renderers write past the vmalloc buffer. Reachability requires access to a framebuffer character device or virtual console; the corruption can disclose or alter kernel memory or panic the system.
The record
- CVE
- CVE-2025-40304
- Published
- Dec 8, 2025
- Updated
- Aug 5, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Dec 8, 2025CVE publishedPublication date reported by the CVE source.
- Aug 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <15ba9acafb0517f8359ca30002c189a68ddbb939
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1943b69e87b0ab35032d47de0a7fca9a3d1d6fc1
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2d1359e11674ed4274934eac8a71877ae5ae7bbb
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3637d34b35b287ab830e66048841ace404382b67
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <86df8ade88d290725554cefd03101ecd0fbd3752
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <996bfaa7372d6718b6d860bdf78f6618e850c702
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ebc0730b490c7f27340b1222e01dd106e820320d
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f0982400648a3e00580253e0c48e991f34d2684c
- Affected versionversion=2.6.12
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- KASAN vmalloc-out-of-bounds Write in imageblit reproducerproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo