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CVE-2026-72351
gue: validate REMCSUM private option length
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72351 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
GUE private flags can indicate that remote checksum offload metadata is present. The private flags field itself is accounted for by guehdr_flags_len(), but guehdr_priv_flags_len() currently returns 0 even when GUE_PFLAG_REMCSUM is set. This lets a packet with only the private flags field pass validate_gue_flags(), after which gue_remcsum() and gue_gro_remcsum() read the missing REMCSUM start/offset fields from the following bytes. Account for GUE_PLEN_REMCSUM when GUE_PFLAG_REMCSUM is present so that malformed packets are rejected during option validation.
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.
include/net/gue.h
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on include/net/ · netdev@vger.kernel.org · Maintained
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
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.
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
Signals
- Published
- 2026-08-15 (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
- 0.74%, higher than 53.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.19 | 5.10.261 | 158b9995d3c8 |
| 3.19 | 5.15.212 | 7c6876ec1b22 |
| 3.19 | 6.1.178 | 2c4de9988e9d |
| 3.19 | 6.6.145 | 2a99224c1208 |
| 3.19 | 6.12.97 | 61e78679c7c9 |
| 3.19 | 6.18.40 | 4a4a1d41c6e9 |
| 3.19 | 7.1.5 | f618cbe9b24c |
| 3.19 | 7.2 | d335dcc6f521 |
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
- Malformed GUE-over-UDP packets reach gue_udp_recv() and gue_gro_receive() through the normal IP/UDP receive path on hosts with FOU/GUE listeners, including internet-facing cloud overlay endpoints.
- AC:LAttack complexity, low
- An attacker fully controls the crafted packet and can set GUE_PFLAG_REMCSUM with only the private-flags option present, reliably triggering gue_remcsum()/gue_gro_remcsum() without races or special timing.
- PR:NPrivileges required, none
- Exploitation requires only sending UDP to a GUE listener port; no target credentials or local privileges are needed by the remote attacker even though tunnel setup itself requires admin configuration.
- UI:NUser interaction, none
- No victim interaction is required beyond the host already receiving GUE tunnel traffic as part of normal overlay networking operation.
- S:UScope, unchanged
- The flaw corrupts kernel packet buffers during GUE receive processing on the target host and does not inherently cross VM, container, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- Missing REMCSUM length validation lets attacker-controlled start/offset drive remcsum_adjust()/csum_partial() to read beyond the declared GUE options into adjacent skb bytes, enabling memory disclosure primitives.
- I:HIntegrity impact, high
- remcsum_adjust() performs an out-of-bounds 2-byte write at ptr+offset, and the default partial-checksum path stores attacker-controlled csum_start/csum_offset metadata that can corrupt subsequent checksum offload handling.
- A:HAvailability impact, high
- Out-of-bounds REMCSUM processing can trigger kernel oops or panic from invalid memory access or corrupted packet state, causing denial of service on overlay endpoints under repeated attack.