Linux Kernel up to 6.12.13/6.13.2 ceph_mds_auth_match memory leak

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 6.12.13/6.13.2. This issue affects the function ceph_mds_auth_match. Executing a manipulation can lead to memory leak. The identification of this vulnerability is CVE-2025-21737. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.13/6.13.2. It has been declared as critical. This vulnerability affects the function ceph_mds_auth_match. The manipulation with an unknown input leads to a memory leak vulnerability. The CWE definition for the vulnerability is CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. As an impact it is known to affect availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ceph: fix memory leak in ceph_mds_auth_match() We now free the temporary target path substring allocation on every possible branch, instead of omitting the default branch. In some cases, a memory leak occured, which could rapidly crash the system (depending on how many file accesses were attempted). This was detected in production because it caused a continuous memory growth, eventually triggering kernel OOM and completely hard-locking the kernel. Relevant kmemleak stacktrace: unreferenced object 0xffff888131e69900 (size 128): comm "git", pid 66104, jiffies 4295435999 hex dump (first 32 bytes): 76 6f 6c 75 6d 65 73 2f 63 6f 6e 74 61 69 6e 65 volumes/containe 72 73 2f 67 69 74 65 61 2f 67 69 74 65 61 2f 67 rs/gitea/gitea/g backtrace (crc 2f3bb450): [] __kmalloc_noprof+0x359/0x510 [] ceph_mds_check_access+0x5bf/0x14e0 [ceph] [] ceph_open+0x312/0xd80 [ceph] [] do_dentry_open+0x456/0x1120 [] vfs_open+0x79/0x360 [] path_openat+0x1de5/0x4390 [] do_filp_open+0x19c/0x3c0 [] do_sys_openat2+0x141/0x180 [] __x64_sys_open+0xe5/0x1a0 [] do_syscall_64+0xb7/0x210 [] entry_SYSCALL_64_after_hwframe+0x77/0x7f It can be triggered by mouting a subdirectory of a CephFS filesystem, and then trying to access files on this subdirectory with an auth token using a path-scoped capability: $ ceph auth get client.services [client.services] key = REDACTED caps mds = "allow rw fsname=cephfs path=/volumes/" caps mon = "allow r fsname=cephfs" caps osd = "allow rw tag cephfs data=cephfs" $ cat /proc/self/mounts services@[REDACTED].cephfs=/volumes/containers /ceph/containers ceph rw,noatime,name=services,secret=,ms_mode=prefer-crc,mount_timeout=300,acl,mon_addr=[REDACTED]:3300,recover_session=clean 0 0 $ seq 1 1000000 | xargs -P32 --replace={} touch /ceph/containers/file-{} && \ seq 1 1000000 | xargs -P32 --replace={} cat /ceph/containers/file-{} [ idryomov: combine if statements, rename rc to path_matched and make it a bool, formatting ]

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2025-21737 since 12/29/2024. The exploitation appears to be difficult. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 236983 (Ubuntu 24.04 LTS / 24.10 : Linux kernel vulnerabilities (USN-7521-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.12.14, 6.13.3 or 6.14-rc1 eliminates this vulnerability. Applying the patch 146109fe936ac07f8f60cd6267543688985b96bc/2b6086c5efe5c7bd6e0eb440d96c26ca0d20d9d7/3b7d93db450e9d8ead80d75e2a303248f1528c35 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (236983) and CERT Bund (WID-SEC-2025-0453). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• Siemens SIMATIC S7
• RESF Rocky Linux
• Dell NetWorker
• Dell Avamar
• Red Hat OpenShift
• IBM QRadar SIEM
• SolarWinds Security Event Manager
• Dell PowerProtect Data Domain
• Open Source Linux Kernel
• IBM DataPower Gateway
• Dell Secure Connect Gateway
• Dell PowerScale OneFS
• Dell ECS

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.13.0
• 6.13.1
• 6.13.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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