Linux kernel: Disable GSO for packets with small MSS on Power adapters
CVE-2026-46273 Published on June 3, 2026
ibmveth: Disable GSO for packets with small MSS
In the Linux kernel, the following vulnerability has been resolved:
ibmveth: Disable GSO for packets with small MSS
Some physical adapters on Power systems do not support segmentation
offload when the MSS is less than 224 bytes. Attempting to send such
packets causes the adapter to freeze, stopping all traffic until
manually reset.
Implement ndo_features_check to disable GSO for packets with small MSS
values. The network stack will perform software segmentation instead.
The 224-byte minimum matches ibmvnic
commit <f10b09ef687f> ("ibmvnic: Enforce stronger sanity checks
on GSO packets")
which uses the same physical adapters in SEA configurations.
The issue occurs specifically when the hardware attempts to perform
segmentation (gso_segs > 1) with a small MSS. Single-segment GSO packets
(gso_segs == 1) do not trigger the problematic LSO code path and are
transmitted normally without segmentation.
Add an ndo_features_check callback to disable GSO when MSS < 224 bytes.
Also call vlan_features_check() to ensure proper handling of VLAN packets,
particularly QinQ (802.1ad) configurations where the hardware parser may
not support certain offload features.
Validated using iptables to force small MSS values. Without the fix,
the adapter freezes. With the fix, packets are segmented in software
and transmission succeeds. Comprehensive regression testing completedd
(MSS tests, performance, stability).
Products Associated with CVE-2026-46273
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Affected Versions
Linux:- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below 86fc64584811d43c9ccd74447de58620189d8b77 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below 9a5e984d7af910e46dcbed3ce77873e000a4f77d is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below 1cdf5dbcec988d06f5f720bdf89e91073f77fa10 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below 82bc89fbb82d9396fb4eaee8720ea85e2e787957 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below db8012c631cb845e9ae2b4b531e17d86c9519755 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below c1f261863e65b508f37416dfbc5c5d911c9b9233 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below 3af24f0c4c31f18a4a2d927990759194832bb6e9 is affected.
- Version 8641dd85799f85bef5f0d1f87356aaa12cb2195e and below cc427d24ac6442ffdeafd157a63c7c5b73ed4de4 is affected.
- Version 4.2 is affected.
- Before 4.2 is unaffected.
- Version 5.10.258, <= 5.10.* is unaffected.
- Version 5.15.209, <= 5.15.* is unaffected.
- Version 6.1.175, <= 6.1.* is unaffected.
- Version 6.6.140, <= 6.6.* is unaffected.
- Version 6.12.88, <= 6.12.* is unaffected.
- Version 6.18.30, <= 6.18.* is unaffected.
- Version 7.0.7, <= 7.0.* is unaffected.
- Version 7.1-rc2, <= * is unaffected.