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CVE-2026-80528
ceph: avoid fs reclaim while using current->journal_info
Published 2026-08-26 (2 months ago) by the Linux kernel CNA. Subsystem fs/ceph. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80528 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.105-1 | Update the kernel and reboot. Fixed in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
handle_reply() stores a `ceph_mds_request` pointer in `current->journal_info` while filling the inode and dentry cache from an MDS reply. An allocation in this section can enter direct reclaim and prune dentries from another filesystem. If this dirties an ext4 inode, ext4 starts a JBD2 transaction. JBD2 interprets the Ceph request in `current->journal_info` as a journal handle and dereferences the request's `r_tid` as `h_transaction`, causing a kernel crash, e.g.: Unable to handle kernel paging request at virtual address 00000000077b4818 [...] Internal error: Oops: 0000000096000004 [#1] SMP Modules linked in: CPU: 6 UID: 0 PID: 2699135 Comm: kworker/6:3 Tainted: G W 6.18.38-i3 #1113 NONE [...] Workqueue: ceph-msgr ceph_con_workfn pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : jbd2__journal_start+0x2c/0x208 lr : __ext4_journal_start_sb+0x100/0x178 [...] Call trace: jbd2__journal_start+0x2c/0x208 (P) __ext4_journal_start_sb+0x100/0x178 ext4_dirty_inode+0x3c/0x90 __mark_inode_dirty+0x58/0x400 iput.part.0+0x2b0/0x370 iput+0x18/0x30 dentry_unlink_inode+0xc0/0x158 __dentry_kill+0x80/0x250 shrink_dentry_list+0x90/0x130 prune_dcache_sb+0x60/0x98 super_cache_scan+0xe8/0x190 do_shrink_slab+0x174/0x388 shrink_slab+0xd8/0x4c0 shrink_node+0x31c/0x908 do_try_to_free_pages+0xd0/0x508 try_to_free_pages+0x11c/0x238 __alloc_frozen_pages_noprof+0x4d0/0xdd0 __folio_alloc_noprof+0x18/0x70 __filemap_get_folio+0x248/0x440 ceph_readdir_prepopulate+0x570/0x9e8 mds_dispatch+0x1424/0x1ba0 ceph_con_process_message+0x74/0xa0 ceph_con_v1_try_read+0x3a0/0x1510 ceph_con_workfn+0x260/0x460 Enter a scoped NOFS allocation context and leave it after clearing `journal_info`. This prevents filesystem reclaim from recursing into another filesystem while the field contains Ceph-private data.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/ceph/mds_client.c
- What this is
- CEPH DISTRIBUTED FILE SYSTEM CLIENT (CEPH)MAINTAINERS section matched on fs/ceph/ · ceph-devel@vger.kernel.org · Supported
- Kernel module
- ceph
Check it on the machine
grep -w CONFIG_CEPH_FS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w cephPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_CEPH_FS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-26 (2 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.51%, higher than 42.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ceph
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.6 | 5.10.266 | ca5fa2380dd9 |
| 4.6 | 5.15.217 | 00c12f57a87f |
| 4.6 | 6.1.184 | 4dbb2c02558e |
| 4.6 | 6.6.153 | c8a21660c3b9 |
| 4.6 | 6.12.105 | 47b745747b3a |
| 4.6 | 6.18.46 | 79d95b43ca09 |
| 4.6 | 7.1.10 | b6a098961307 |
| 4.6 | 7.2 | 5b602344a49e |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The crash path runs in the ceph-msgr kworker handling CEPH_MSG_CLIENT_REPLY from the MDS over TCP; on Ceph/Rook/Kubernetes nodes with cephfs mounted, a compromised or malicious MDS peer drives handle_reply() remotely without requiring a victim syscall.
- AC:LAttack complexity, low
- A MDS peer can supply large readdir/lookup replies to force GFP_KERNEL allocations in ceph_fill_trace/ceph_readdir_prepopulate while journal_info is set, making direct reclaim into ext4 dentry pruning likely without rare kernel configs or uncontrollable heap layout.
- PR:NPrivileges required, none
- Exploitation requires no Linux UID, capability, or init-namespace root on the victim; any kernel cephfs client already connected to an attacker-controlled or compromised cluster suffices, consistent with other MDS-reply client CVEs (e.g., CVE-2026-80527).
- UI:NUser interaction, none
- Once cephfs is mounted (standard in Ceph deployments), MDS replies are processed automatically in kworker context; attackers need not induce a victim to mount media or perform a one-off interactive step at exploitation time.
- S:UScope, unchanged
- Impact is a kernel oops from JBD2 mistyping current->journal_info on the same host; it does not cross VM, container, or IOMMU boundaries to another security authority.
- C:HConfidentiality impact, high
- While journal_info holds a ceph_mds_request pointer, ext4 reclaim invokes jbd2__journal_start(), type-confusing that object as a journal handle and dereferencing r_tid as h_transaction—a cross-subsystem type confusion with kernel-pointer read potential per CNA memory-safety guidance.
- I:HIntegrity impact, high
- Type confusion of current->journal_info between Ceph and JBD2 misinterprets live ceph_mds_request fields as journal-handle metadata during MDS reply processing; kernel CNA guidance classes type confusion as High integrity impact even when the immediate fault is an oops.
- A:HAvailability impact, high
- The reported ARM64 oops in jbd2__journal_start() from invalid h_transaction dereference reliably crashes the ceph-msgr worker and can panic the node; reclaim during MDS reply handling enables repeated remote-triggered denial-of-service.