{"id":"CVE-2026-68123","state":"PUBLISHED","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.","publishedAt":"2026-08-10T11:58:43.727Z","updatedAt":"2026-10-19T20:58:51.936Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"50a6a85f3d6b1d22d8436848606cdef5d2c490b4","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"2623c48cc3a8da9a1886fd8f65c0e348f4406fd6","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"e211b081901ffca76674082c73eeaed53524c369","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"100a23b1613e9218e0af654ef102352c713f0263","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"ea85dbcbe8d4056ecb54352f97743d138ea4c407","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"4032f8ed10fcb84d41c508dfb04be96589f78dfe","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/openvswitch/actions.c","net/openvswitch/datapath.c","net/openvswitch/datapath.h","net/openvswitch/vport.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.8","versionType":"semver"},{"version":"5.10.265","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/openvswitch/actions.c","net/openvswitch/datapath.c","net/openvswitch/datapath.h","net/openvswitch/vport.c"]}],"references":["https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4","https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6","https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369","https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855","https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc","https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263","https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407","https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe"],"weaknesses":["CWE-191"],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/68xxx/CVE-2026-68123.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68123","state":"PUBLISHED","datePublished":"2026-08-10T11:58:43.727Z","dateUpdated":"2026-10-19T20:58:51.936Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-30T09:28:09.369Z"},"containers":{"cna":{"title":"openvswitch: fix GSO userspace truncation underflow","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"50a6a85f3d6b1d22d8436848606cdef5d2c490b4","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"2623c48cc3a8da9a1886fd8f65c0e348f4406fd6","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"e211b081901ffca76674082c73eeaed53524c369","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"100a23b1613e9218e0af654ef102352c713f0263","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"ea85dbcbe8d4056ecb54352f97743d138ea4c407","versionType":"git"},{"version":"f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1","status":"affected","lessThan":"4032f8ed10fcb84d41c508dfb04be96589f78dfe","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/openvswitch/actions.c","net/openvswitch/datapath.c","net/openvswitch/datapath.h","net/openvswitch/vport.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.8","versionType":"semver"},{"version":"5.10.265","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/openvswitch/actions.c","net/openvswitch/datapath.c","net/openvswitch/datapath.h","net/openvswitch/vport.c"]}],"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"}],"metrics":[{"cvssV3_1":{"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"},"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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-19T16:29:34.391Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"5.10.265"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-68123","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:44:13.520896Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-191","lang":"en","type":"CWE","description":"CWE-191 Integer Underflow (Wrap or Wraparound)"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:58:51.936Z"}}]}}}