Improper Verification of Cryptographic Signature in Ceph - CVE-2026-39944
Published: August 19, 2026
Vulnerability identifier: #VU144399
CSH Severity: Medium
CVSS v4: 7.7 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-39944
CWE-ID: CWE-347
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to escalate privileges to full RGW administrative access.
The vulnerability exists due to improper verification of a cryptographic signature in RGW STS session tokens when processing a valid STS token. A remote user can tamper with a token using CBC bit-flipping to escalate privileges to full RGW administrative access.
Exploitation requires STS to be enabled and a single valid STS token already held by the attacker.
Affected software
Ceph
How to mitigate CVE-2026-39944
Install security update from vendor's website.
Ceph - addressed in versions 19.2.6, 20.2.4