{"api_version":"1","generated_at":"2026-08-23T04:03:34+00:00","cve":"CVE-2026-68123","urls":{"html":"https://cve.report/CVE-2026-68123","api":"https://cve.report/api/cve/CVE-2026-68123.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-68123","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-68123"},"summary":{"title":"openvswitch: fix GSO userspace truncation underflow","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: fix GSO userspace truncation underflow\n\nOVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb\nlength in OVS_CB(skb)->cutlen. When a later userspace action segments a\nGSO skb, queue_gso_packets() reuses that delta for each smaller segment.\nA segment can then reach queue_userspace_packet() with cutlen greater\nthan skb->len, underflowing the length passed to skb_zerocopy().\n\nStore the maximum preserved length instead and bound each consumer\nagainst the current skb length. Use U32_MAX as the no-truncation\nsentinel so the value remains valid if skb geometry changes before a\nconsumer handles it.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-10 13:19:57","updated_at":"2026-08-19 17:20:29"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407","name":"https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855","name":"https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe","name":"https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369","name":"https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263","name":"https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6","name":"https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4","name":"https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc","name":"https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-68123","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68123","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 50a6a85f3d6b1d22d8436848606cdef5d2c490b4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 2623c48cc3a8da9a1886fd8f65c0e348f4406fd6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 e211b081901ffca76674082c73eeaed53524c369 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: fix GSO userspace truncation underflow\n\nOVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb\nlength in OVS_CB(skb)->cutlen. When a later userspace action segments a\nGSO skb, queue_gso_packets() reuses that delta for each smaller segment.\nA segment can then reach queue_userspace_packet() with cutlen greater\nthan skb->len, underflowing the length passed to skb_zerocopy().\n\nStore the maximum preserved length instead and bound each consumer\nagainst the current skb length. Use U32_MAX as the no-truncation\nsentinel so the value remains valid if skb geometry changes before a\nconsumer handles it."}],"metrics":[{"cvssV3_1":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - Ingress packets reach ovs_vport_receive() through netdev rx_handlers or tunnel vports; GRO-coalesced GSO skbs from remote senders traverse this path into queue_gso_packets(), so the underflow is reachable from the network without physical access.\nAC:L - The attacker chooses truncation max_len relative to GSO super-skb size and sends traffic that GRO segments predictably; no timing race or fragile heap layout is required to make cutlen exceed a child segment length after __skb_gso_segment().\nPR:N - In multi-tenant cloud/OVN deployments, a remote VM or container can send crafted GSO traffic into the host OVS datapath to hit provider-installed TRUNC+USERSPACE sampling flows without possessing any Linux capabilities on the host.\nUI:N - Triggering the flaw requires only network traffic matching existing OVS flow actions; no victim login, file open, mount, or other interactive step is needed.\nS:U - Impact is kernel memory corruption and crash/escalation within the host kernel security domain; it does not cross a guest-to-hypervisor, VM, or hardware IOMMU trust boundary by itself.\nC:H - Unsigned underflow makes skb->len-cutlen enormous for skb_zerocopy()/skb_copy_bits(), enabling out-of-bounds reads from the source skb and adjacent slab data, i.e., an exploitable information-disclosure primitive.\nI:H - The same underflowed length can expand destination skbs via skb_len_add()/nlattr sizing, corrupting kernel heap metadata and yielding a write primitive suitable for control-flow hijacking.\nA:H - The miscopied lengths can BUG the skb helpers or cause immediate kernel oops/panic during zerocopy/trim handling, and corrupted metadata can crash the system even if exploitation is not completed."}]}],"providerMetadata":{"dateUpdated":"2026-08-19T16:29:34.391Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4"},{"url":"https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6"},{"url":"https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369"},{"url":"https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855"},{"url":"https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc"},{"url":"https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263"},{"url":"https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407"},{"url":"https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe"}],"title":"openvswitch: fix GSO userspace truncation underflow","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-68123","datePublished":"2026-08-10T11:58:43.727Z","dateReserved":"2026-07-30T09:28:09.369Z","dateUpdated":"2026-08-19T16:29:34.391Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-10 13:19:57","lastModifiedDate":"2026-08-19 17:20:29","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"68123","Ordinal":"1","Title":"openvswitch: fix GSO userspace truncation underflow","CVE":"CVE-2026-68123","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"68123","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: fix GSO userspace truncation underflow\n\nOVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb\nlength in OVS_CB(skb)->cutlen. When a later userspace action segments a\nGSO skb, queue_gso_packets() reuses that delta for each smaller segment.\nA segment can then reach queue_userspace_packet() with cutlen greater\nthan skb->len, underflowing the length passed to skb_zerocopy().\n\nStore the maximum preserved length instead and bound each consumer\nagainst the current skb length. Use U32_MAX as the no-truncation\nsentinel so the value remains valid if skb geometry changes before a\nconsumer handles it.","Type":"Description","Title":"openvswitch: fix GSO userspace truncation underflow"}]}}}