CVE-2025-47711: Nbdkit: nbdkit-server: off-by-one error when processing block status may lead to a denial of service

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-06-09 · updated 2026-06-30
Weakness: CWE-193

Description

There's a flaw in the nbdkit server when handling responses from its plugins regarding the status of data blocks. If a client makes a specific request for a very large data range, and a plugin responds with an even larger single block, the nbdkit server can encounter a critical internal error, leading to a denial-of-service.

Affected products

nbdkit: all versions
Red Hat Enterprise Linux: 7.0, 8.0, 9.0, 10.0
RedHat Enterprise Linux Advanced Virtualization: 8.0

References

https://access.redhat.com/security/cve/CVE-2025-47711
https://bugzilla.redhat.com/show_bug.cgi?id=2365687
https://lists.libguestfs.org/archives/list/guestfs@lists.libguestfs.org/thread/67E7AASHHADIY7VAD3FFW2I67LTWVWYF/

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