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Fencer Vulns
high 8.8

CVE-2026-39944 json

Ceph: CephX AES Authentication error

published 2026-08-27 2 mo ago modified 2026-09-08 2 mo ago also BIT-ceph-2026-39944 , EUVD-2026-67315 , GHSA-j73r-qrgx-jvq2

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits
0
none known

Summary

Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the RADOS Gateway (RGW) protects STS session tokens with an AES-128-CBC handler that provides no message authentication, allowing an attacker who holds any valid STS token to tamper with it undetected and escalate to full RGW administrative access. Because the ciphertext is unauthenticated, the attacker can perform a CBC bit-flip on the acct_type, perm_type, and is_admin fields of their own token, and a forged is_admin value triggers a global administrative override that bypasses all capability checks. The attack is reachable remotely over the RGW S3 endpoint and is a self-contained modification of a token the attacker already possesses, requiring no encryption oracle and no network observation. It requires only a single valid STS token, which need not carry any elevated privileges, with STS enabled. This issue is fixed in versions 20.2.4 and 19.2.6.

Patch / fix

  • bitnami ceph 19.2.6, 20.2.4
  • linuxfoundation ceph 19.2.6, 20.2.4
  • redhat ceph 19.2.6, 20.2.4
  • ceph Debian 14 20.2.4+ds-1

debian advisories DEBIAN-CVE-2026-39944

  • ceph ceph storage 8.1 2:19.2.1-423.el9cp
  • cephadm ceph storage 8.1 2:19.2.1-423.el9cp
  • librbd1 ceph storage 8.1 2:19.2.1-423.el9cp
  • librgw2 ceph storage 8.1 2:19.2.1-423.el9cp
  • rbd-nbd ceph storage 8.1 2:19.2.1-423.el9cp
  • ceph-mib ceph storage 8.1 2:19.2.1-423.el9cp
  • ceph-base ceph storage 8.1 2:19.2.1-423.el9cp
  • ceph-fuse ceph storage 8.1 2:19.2.1-423.el9cp

red hat advisories RHSA-2026:79101

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-39944 updated cvss 8.5

ceph: ceph: RGW STS session tokens vulnerable to CBC bit-flip attack enabling admin privilege escalation

  • Red Hat Ceph Storage 4 ceph, librbd1, librgw2, rbd-nbd, ceph-mds, ceph-mgr, +27 more Red Hat Ceph Storage 5 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mds, +33 more Red Hat Ceph Storage 6 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mib, +16 more Red Hat Ceph Storage 7 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mib, +17 more Red Hat Ceph Storage 9 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mib, +18 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Ceph Storage 8.1 rhceph/rhceph-8-rhel9 1791176990
    fixed: vendor fix RHSA-2026:79243
  • Red Hat Ceph Storage 8.1 Tools ceph 19.2.1-423.el9cp, cephadm 19.2.1-423.el9cp, librbd1 19.2.1-423.el9cp, librgw2 19.2.1-423.el9cp, rbd-nbd 19.2.1-423.el9cp, ceph-mib 19.2.1-423.el9cp, +17 more
    fixed: vendor fix RHSA-2026:79101
  • Red Hat Ceph Storage 8.1 rhceph/grafana-rhel9 1791176238, rhceph/keepalived-rhel9 1791175257, rhceph/oauth2-proxy-rhel9 1791176282, rhceph/snmp-notifier-rhel9 1791176336, rhceph/rhceph-haproxy-rhel9 1791176338, rhceph/rhceph-promtail-rhel9 1791176366
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 mo ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
OSV 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
bitnami ceph
>=19.0.0, <19.2.6
>=20.0.0, <20.2.4
19.2.6
20.2.4

Affected products

  • ceph ceph

Classification

Weakness
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.