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Linux KernelOperating system · Linux

CVE-2026-52956

HIGH · 7.5 CVSS v3.1 Published 2026-06-24
Fix available
A fix is available. Upgrade to 4.10 / 7.0.10 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: libceph: Fix potential out-of-bounds access in __ceph_x_decrypt() In __ceph_x_decrypt(), a part of the buffer p is interpreted as a ceph_x_encrypt_header, and the magic field of this struct is accessed. This happens without any guarantee that the buffer is large enough to hold this struct. The function parameter ciphertext_len represents the length of the ciphertext to decrypt and is guaranteed to be at most the remaining size of the allocated buffer p. However, this value is not necessarily greater than sizeof(ceph_x_encrypt_header). E.g., a message frame of type FRAME_TAG_AUTH_REPLY_MORE, that is just as long to hold the ciphertext at its end with a ciphertext_len of 8 or less, can trigger an out-of-bounds memory access when accessing hdr->magic. This patch fixes the issue by adding a check to ensure that the decrypted plaintext in the buffer is large enough to represent at least the ceph_x_encrypt_header.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In the Linux kernel's libceph module, the __ceph_x_decrypt() function accesses a buffer as a ceph_x_encrypt_header struct without validating that the buffer is large enough to hold it. Specifically, the hdr->magic field is accessed when ciphertext_len may be smaller than sizeof(ceph_x_encrypt_header). This out-of-bounds read can be triggered by crafted Ceph messages with small ciphertext_len values (8 or less), such as FRAME_TAG_AUTH_REPLY_MORE frames.

MitigationApply the kernel patch which adds a bounds check to verify the plaintext buffer is large enough to contain the ceph_x_encrypt_header before dereferencing hdr->magic. Update to a kernel version containing this fix.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.9.6, < 4.10>= 4.10, < 7.0.10= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run 'uname -r' or 'cat /proc/version' to obtain the running kernel version
    Affected if The kernel version falls within >= 4.9.6 and < 4.10, OR >= 4.10 and < 7.0.10, OR equals 7.1
  2. Verify libceph kernel module is loaded
    Run 'lsmod | grep ceph' or check /sys/module/ for ceph-related modules
    Affected if The ceph, libceph, or related kernel modules are loaded, indicating Ceph client functionality is in use
  3. Check for Ceph configuration
    Look for /etc/ceph/ directory or ceph.conf configuration file, and check for cephx authentication key files in /etc/ceph/
    Affected if Ceph configuration exists and the system is configured to communicate with Ceph clusters
  4. Inspect Ceph network connections
    Run 'ss -tnp' or 'netstat -tnp' to identify active connections to Ceph monitor or OSD ports (ports 3300, 6789, and 6800-7300)
    Affected if The system has active network connections to Ceph endpoints, enabling the attack vector
  5. Verify Ceph authentication messages
    Capture network traffic using tcpdump on Ceph ports during authentication handshake, specifically looking for FRAME_TAG_AUTH_REPLY_MORE message frames
    Affected if Untrusted Ceph endpoints are reachable and the system performs Ceph authentication exchanges

The system is affected if the kernel version is in the vulnerable range AND libceph is actively used to communicate with Ceph endpoints, allowing specially crafted authentication reply messages to trigger the out-of-bounds read.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.10 / 7.0.10 or later
Fixed in 4.107.0.10
Interim mitigation

Apply the kernel patch which adds a bounds check to verify the plaintext buffer is large enough to contain the ceph_x_encrypt_header before dereferencing hdr->magic. Update to a kernel version containing this fix.

Recommended fix Moderate confidence

Linux Kernel 7.0.10 or later stable release

  1. 1. Identify the current running kernel version using `uname -r`
  2. 2. Check if the current version is affected: versions >= 4.9.6 and < 4.10, or >= 4.10 and < 7.0.10, or exactly 7.1
  3. 3. Plan a kernel upgrade to a fixed release (7.0.10 or later point release) that includes the patch for the out-of-bounds read in __ceph_x_decrypt()
  4. 4. Before upgrading in production, test the new kernel in a staging environment to ensure compatibility with hardware and workloads
  5. 5. Apply the upgrade using the distribution's standard kernel update process (e.g., `apt-get dist-upgrade`, `yum update`, or vendor-specific tools)
  6. 6. Reboot into the new kernel and verify the system boots successfully
  7. 7. Verify the fix is present by checking that the ceph module loads without errors and libceph functionality works correctly
Caveat Kernel upgrades may require updated drivers or firmware; ensure compatibility with hardware and check for any required configuration changes for the ceph subsystem

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,540
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52956 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data