CVE-2023-0266
CVE-2023-0266 is a security flaw in Linux Kernel, the core of Linux, which runs most servers, Android phones and many home routers. Someone who already has a foothold can use Linux Kernel to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 30 Mar 2023.[1]
Linux Kernel is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed by a commit to Linux Kernel, in the releases that include it.
Description
CISA calls it an use-after-free in Linux Kernel. In its words: “Linux kernel contains a use-after-free vulnerability that allows for privilege escalation to gain ring0 access from the system user.”[1]
The CVE record adds: “A use after free vulnerability exists in the ALSA PCM package in the Linux Kernel. SNDRV_CTL_IOCTL_ELEM_{READ|WRITE}32 is missing locks that can be used in a use-after-free that can result in a priviledge escalation to gain ring0 access from the system user. We recommend upgrading past commit 56b88b50565cd8b946a2d00b0c83927b7ebb055e”[2]
The underlying weakness is use after free (CWE-416), in MITRE’s list of common software weaknesses.
It scores 7.0 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists one fixed version: everything before it is affected.[2]
| Product | Fixed in |
|---|---|
| Linux Kernel | commit 56b88b50565c |
Most families won’t have Linux Kernel; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 30 Mar 2023, 59 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 20 Apr 2023 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 4%. That’s in the top 11% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Linux has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Linux Kernel is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed by a commit to Linux Kernel, in the releases that include it), or not in use. CISA gave US government agencies until 20 Apr 2023 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.0.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 4%.[4] |
See also
Other Linux Kernel flaws
- CVE-2026-46300: missing initialization of a variable ·
- CVE-2026-53266: out-of-bounds write ·
- CVE-2025-39964: race condition ·
- CVE-2025-39682: improper check for unusual or exceptional conditions ·
- CVE-2026-53362: unspecified ·
- CVE-2022-0995: out-of-bounds write ·
Other use after free flaws
- CVE-2026-109619, PHP: stale internal request-state ·
- CVE-2026-109618, PHP: memory corruption ·
- CVE-2026-68820, Microsoft Windows Ancillary Function Driver for WinSock: use-after-free ·
- CVE-2010-0249, Microsoft Internet Explorer: use-after-free ·
- CVE-2020-9715, Adobe Acrobat: use-after-free ·
Added the same day
- CVE-2022-42948, Fortra Cobalt Strike: user interface remote code execution ·
- CVE-2022-39197, Fortra Cobalt Strike: teamserver cross-site scripting (XSS) ·
- CVE-2022-38181, Arm Mali Graphics Processing Unit (GPU): mali GPU kernel driver use-after-free ·
- CVE-2022-3038, Chrome and other Chromium browsers: use-after-free ·
- CVE-2022-22706, Arm Mali Graphics Processing Unit (GPU): mali GPU kernel driver unspecified ·
Every Linux flaw on CISA’s list · Everything added in March 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Linux Kernel Use-After-Free Vulnerability”. Known Exploited Vulnerabilities Catalog, added 30 Mar 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-0266 Detail”. National Vulnerability Database, published 30 Jan 2023.
- ^ Linux. Advisories and fixes: git.kernel.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.037, percentile 89.7, 31 Oct 2026.
- CVE Program. “CVE-2023-0266”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.