CVE-2023-5215: Red Hat Enterprise Linux 9 · Improper Handling of Unexpected Data Type
Affects Red Hat Enterprise Linux 9Source CVE Database V5
Not known to be exploited · CVSS 5.3 Medium.
Data as of 26 Oct 2026, 10:12 UTC
- EPSS
- 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 28 Sep 2023
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
AI-suggested
European organizations should prioritize updating libnbd to the latest patched version as soon as it becomes available from Red Hat or the libnbd maintainers. In the interim, administrators should audit and harden NBD client implementations to ensure they properly validate the block size returned by nbd_get_size(), rejecting or safely handling values exceeding the protocol specification. Network segmentation and filtering can limit exposure by restricting access to NBD servers to trusted hosts only. Monitoring and alerting on abnormal NBD traffic or client crashes can provide early detection of exploitation attempts. Additionally, organizations should review their incident response plans for storage-related service disruptions and conduct testing to verify resilience against malformed NBD responses. Where feasible, consider alternative storage protocols or clients with proven robustness against such input validation issues.
Description
A flaw was found in libnbd. A server can reply with a block size larger than 2^63 (the NBD spec states the size is a 64-bit unsigned value). This issue could lead to an application crash or other unintended behavior for NBD clients that doesn't treat the return value of the nbd_get_size() function correctly.