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CVE-2026-53363
xfrm: iptfs: preserve shared-frag marker in iptfs_consume_frags()
Published 2026-07-10 (3 months ago) by the Linux kernel CNA. Subsystem net/xfrm. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53363 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
iptfs_consume_frags() transfers paged fragments from one socket buffer to another but fails to propagate the SKBFL_SHARED_FRAG flag. This is the same class of bug that was fixed in skb_try_coalesce() for CVE-2026-46300: when fragments backed by read-only page-cache pages are merged, the marker indicating their shared nature must be preserved so that ESP can decide correctly whether in-place encryption is safe. Apply the same two-line fix used in skb_try_coalesce() to iptfs_consume_frags().
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.
net/xfrm/xfrm_iptfs.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_XFRM|CONFIG_XFRM_IPTFS' /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.
Show whether Debian builds this, per release
Debian does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_XFRM, CONFIG_XFRM_IPTFS
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-07-10 (3 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
- 0.32%, higher than 23.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/xfrm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.14 | 6.18.36 | dd66f7f6e360 |
| 6.14 | 7.0.13 | c885d111ed9f |
| 6.14 | 7.1 | e9096a5a170e |
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
- An unauthenticated remote peer can trigger the vulnerable outbound IP-TFS ESP aggregation path by causing a network service to send file-backed splice/sendfile data through an already configured IP-TFS tunnel. A local user namespace setup is also possible, but Network is the higher defensible vector.
- AC:LAttack complexity, low
- No race or uncontrollable timing is required; the attacker can shape request sizes and traffic volume so shared-frag skbs are aggregated before ESP processing. The required IP-TFS configuration is the vulnerable operating mode, not an exploitation complexity barrier.
- PR:NPrivileges required, none
- The remote-service scenario requires no attacker privileges once the target already uses IP-TFS/IPsec for that traffic. Although creating XFRM state requires CAP_NET_ADMIN, that gate is not crossed by the remote attacker and is also namespace-reachable for local reproduction.
- UI:NUser interaction, none
- No human action is needed after the affected tunnel/service is running. Packets and service responses drive the vulnerable path automatically.
- S:UScope, unchanged
- The corruption occurs within the same kernel/system security authority and does not cross a VM, IOMMU, or separate sandbox boundary. Standard kernel or page-cache compromise remains Scope Unchanged.
- C:HConfidentiality impact, high
- The lost marker permits ESP crypto to operate on externally owned/page-cache-backed fragments as if privately owned, creating cross-object memory corruption in kernel-managed cache pages. Under the required higher-severity assumption, that corruption can support sensitive data exposure or further exploitation.
- I:HIntegrity impact, high
- Similar shared-frag fixes explicitly describe writes into the page cache of root-owned read-only files; this bug preserves that class of externally backed page corruption through IP-TFS aggregation. That is a high-integrity impact because attacker-influenced crypto output can modify data outside the skb’s ownership.
- A:HAvailability impact, high
- Corrupting page-cache-backed executable, library, or service data can crash or destabilize privileged processes and repeatedly disrupt the affected system. Kernel-managed memory corruption is therefore a high availability impact.