CVE-2026-23255: Linux kernel · net: add proper RCU protection to /proc/net/ptype
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 15:59 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 18 Mar 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
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1020.22?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1018.18?arch=source&distro=questingOther 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 addressing this vulnerability is available and should be applied. The vendor advisory from Ubuntu confirms that this issue has been fixed in updated Linux kernel packages. Users should update to the fixed kernel versions to mitigate the risk. No additional mitigation steps are indicated or required beyond applying the official fix.
Description
A vulnerability in the Linux kernel related to improper Read-Copy-Update (RCU) protection in the /proc/net/ptype interface has been resolved. The issue involves ptype_seq_show() and ptype_seq_next() functions violating RCU rules, potentially causing an RCU stall. Concurrent modifications to packet_type structures without proper synchronization could lead to use-after-free conditions. A patch was introduced to add proper RCU protection and safely handle device pointers during iteration.
References
- ubuntu.com/security/CVE-2026-23255 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23255 (opens in a new tab)
- git.kernel.org/linus/f613e8b4afea0cd17c7168e8b00e25bc8d33175d (opens in a new tab)
- git.kernel.org/stable/c/589a530ae44d0c80f523fcfd1a15af8087f27d35 (opens in a new tab)
- git.kernel.org/stable/c/f613e8b4afea0cd17c7168e8b00e25bc8d33175d (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8606-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8607-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8608-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8609-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8619-1 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-23255 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- git.kernel.org/stable/c/002a73470b56848e4c81efeaaedd471e92d66d8d (opens in a new tab)
- git.kernel.org/stable/c/dcefd3f0b9ed8288654c75254bdcee8e1085e861 (opens in a new tab)
- git.kernel.org/stable/c/e974a10a52618f7f57a4bce173a0ed96acd4e5dc (opens in a new tab)