CVE-2026-98621
In the Linux kernel, the following vulnerability has been resolved: net: gue: reject invalid REMCSUM offsets The REMCSUM option carries an absolute checksum start and checksum field offset. gue_remcsum() passes them to skb_remcsum_process(), whose partial path stores offset - start in the u16 skb->csum_offset variable. If offset is less than start, this underflows. A forwarded packet can retain CHECKSUM_PARTIAL and reach a NETIF_F_HW_CSUM driver which trusts the metadata, leading skb_copy_and_csum_dev() to write two bytes about 64 KiB beyond the destination buffer. Reject reversed tuples in validate_gue_flags(), after the existing length validation, so all GUE parsers enforce the ordering in one place.
Affected versions
Linux kernel versions
4.0
and later are affected. Fixed in
5.10.271,
5.15.222,
6.1.189,
6.6.158,
6.12.112,
6.18.55,
7.2.9,
7.3
and their respective stable series.
References
8 totalFrequently asked questions
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What is CVE-2026-98621?
CVE-2026-98621 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 4.0 onward and has been patched in 5.10.271, 5.15.222, 6.1.189 and others. CVE-2026-98621 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-98621?
Yes. CVE-2026-98621 has been patched. Fixed versions include 5.10.271, 5.15.222, 6.1.189 and others. If you are running Linux kernel 4.0 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-98621 actively exploited?
No. CVE-2026-98621 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.