{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98393","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.346Z","datePublished":"2026-10-14T13:25:56.697Z","dateUpdated":"2026-10-19T09:18:46.601Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-19T09:18:46.601Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv4: Fix UDP length overflow with PMTU discover and big MTU\n\nThis commit bounds cork->base.fragsize to IP_MAX_MTU to avoid a\npossible overflow of UDP length that triggers a WARN in\nudp_set_len_short when setsockopt IP_MTU_DISCOVER is set to\nIP_PMTUDISC_PROBE, and a large packet is sent over a netdev with an\nunusually large MTU.\n\nSteps to reproduce:\n\n1. Set device MTU bigger than IP_MAX_MTU + 20. cork->base.fragsize will\n   be set to that MTU in ip_setup_cork.\n2. Set IP_MTU_DISCOVER to IP_PMTUDISC_PROBE. It lets maxnonfragsize be\n   set to device MTU (cork->fragsize) in __ip_append_data, rather than\n   to IP_MAX_MTU.\n3. Send 65528 bytes of payload (+8 bytes of UDP header, +20 bytes of\n   IPv4 header). Device MTU allows it (it's only one byte bigger than\n   IP_MAX_MTU + IPv4 header, and the device MTU is bigger than that).\n4. The UDP length in the built packet is 65536, which overflows the\n   16-bit length field and triggers the WARN in udp_set_len_short.\n\nNote: IP_PMTUDISC_DO with IPv4 is safe, because ip_dst_mtu_maybe_forward\nalways clamps at IP_MAX_MTU, unlike ip6_dst_mtu_maybe_forward.\n\nThe Fixes tag points at the first commit where I could reproduce the\noverflow with IPv4 and IP_PMTUDISC_PROBE."}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_output.c"],"versions":[{"version":"daba287b299ec7a2c61ae3a714920e90e8396ad5","lessThan":"83fedc4741210f75be8ca5b487985a242bf6f18d","status":"affected","versionType":"git"},{"version":"daba287b299ec7a2c61ae3a714920e90e8396ad5","lessThan":"81f540827d243b8dad76c1f44e70ea31719f393c","status":"affected","versionType":"git"},{"version":"daba287b299ec7a2c61ae3a714920e90e8396ad5","lessThan":"b83641e0ab8b20eefcc4cdc5a059f897375291a2","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_output.c"],"versions":[{"version":"3.13","status":"affected"},{"version":"0","lessThan":"3.13","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.13","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.13","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.13","versionEndExcluding":"7.3"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/83fedc4741210f75be8ca5b487985a242bf6f18d"},{"url":"https://git.kernel.org/stable/c/81f540827d243b8dad76c1f44e70ea31719f393c"},{"url":"https://git.kernel.org/stable/c/b83641e0ab8b20eefcc4cdc5a059f897375291a2"}],"title":"net: ipv4: Fix UDP length overflow with PMTU discover and big MTU","x_generator":{"engine":"bippy-1.2.0"}}}}