CVE-2026-63956: Linux kernel · USB: serial: cypress_m8: fix memory corruption with small endpoint
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.15.0-1117.124~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 14:05 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +65
Exploitation evidence
Disclosed: evidence found.
CVE published 20 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available and has been included in recent Ubuntu kernel updates. Users should update their Linux kernel to the fixed versions and reboot their systems to apply the fix. No additional mitigation steps are required beyond applying the official patch.
Description
A memory corruption vulnerability in the Linux kernel's USB serial driver for Cypress M8 devices has been fixed. The flaw occurs when the interrupt-out endpoint max packet size is smaller than eight bytes, potentially allowing user-controlled slab corruption or NULL-pointer dereference. This vulnerability affects multiple Linux kernel versions prior to certain patched releases. A patch is available and included in recent Ubuntu kernel updates. Users are advised to update and reboot to apply the fix.
References
- nvd.nist.gov/vuln/detail/CVE-2026-63956 (opens in a new tab)
- git.kernel.org/stable/c/1ef25704bd3b625fd151c09feee459479f71ee64 (opens in a new tab)
- git.kernel.org/stable/c/284105c40fc31fff90cdab8a0377aaeb92f87f0e (opens in a new tab)
- git.kernel.org/stable/c/4bcaa59f403dbde6328604a500d65ee8d40975d9 (opens in a new tab)
- git.kernel.org/stable/c/4fcb22218f0a7229b7ce3b3952fb644def293fa5 (opens in a new tab)
- git.kernel.org/stable/c/52e18ae0c47c5c89e18fcd8022f287f7cc8802ec (opens in a new tab)
- git.kernel.org/stable/c/6c13f3bb652bc8665e709ba07122612586aea648 (opens in a new tab)
- git.kernel.org/stable/c/ad3d1628a46134276546d7a12fedf04be9979158 (opens in a new tab)
- git.kernel.org/stable/c/e1a9d791fd66ab2431b9e6f6f835823809869047 (opens in a new tab)
- ubuntu.com/security/CVE-2026-63956 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-63956 (opens in a new tab)
- git.kernel.org/linus/e1a9d791fd66ab2431b9e6f6f835823809869047 (opens in a new tab)
- ubuntu.com/security/notices/USN-8593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8603-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8618-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8663-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8664-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8903-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8905-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8906-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8904-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8903-2 (opens in a new tab)