{"id":"CVE-2026-64132","state":"PUBLISHED","title":"ipv6: ioam: refresh hdr pointer before ioam6_event()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: ioam: refresh hdr pointer before ioam6_event()\n\nReported by Sashiko:\n\nIn ipv6_hop_ioam(), the hdr pointer is initialized to point into the\nskb's linear data buffer. Later, the code calls skb_ensure_writable(),\nwhich might reallocate the buffer:\n\n\tif (skb_ensure_writable(skb, optoff + 2 + hdr->opt_len))\n\t\tgoto drop;\n\n\t/* Trace pointer may have changed */\n\ttrace = (struct ioam6_trace_hdr *)(skb_network_header(skb)\n\t\t\t\t\t   + optoff + sizeof(*hdr));\n\n\tioam6_fill_trace_data(skb, ns, trace, true);\n\n\tioam6_event(IOAM6_EVENT_TRACE, dev_net(skb->dev),\n\t\t    GFP_ATOMIC, (void *)trace, hdr->opt_len - 2);\n\nIf the skb is cloned or lacks sufficient linear headroom,\nskb_ensure_writable() will invoke pskb_expand_head(), which reallocates\nthe skb's data buffer and frees the old one, invalidating pointers to\nit. While the code recalculates the trace pointer immediately after the\ncall to skb_ensure_writable(), it fails to recalculate the hdr pointer.\n\nThis patch fixes the above by recalculating the hdr pointer before\npassing hdr->opt_len to ioam6_event(), so that we avoid any UaF.","publishedAt":"2026-07-19T15:40:27.590Z","updatedAt":"2026-08-05T12:39:34.060Z","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":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"769723124b7c3b2bfea4cf68ad292698b87c8d01","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"24de676da63c1122d2c13b0d546238b66d1b4e62","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"5af905aa8e91ff8d94572a1e089558f21dcf24ed","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"e46e6bc97fb1f339730ff1ba74267fbf48e7a422","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"]}],"references":["https://git.kernel.org/stable/c/769723124b7c3b2bfea4cf68ad292698b87c8d01","https://git.kernel.org/stable/c/24de676da63c1122d2c13b0d546238b66d1b4e62","https://git.kernel.org/stable/c/5af905aa8e91ff8d94572a1e089558f21dcf24ed","https://git.kernel.org/stable/c/e46e6bc97fb1f339730ff1ba74267fbf48e7a422"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64132.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64132","state":"PUBLISHED","datePublished":"2026-07-19T15:40:27.590Z","dateUpdated":"2026-08-05T12:39:34.060Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.036Z"},"containers":{"cna":{"title":"ipv6: ioam: refresh hdr pointer before ioam6_event()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: ioam: refresh hdr pointer before ioam6_event()\n\nReported by Sashiko:\n\nIn ipv6_hop_ioam(), the hdr pointer is initialized to point into the\nskb's linear data buffer. Later, the code calls skb_ensure_writable(),\nwhich might reallocate the buffer:\n\n\tif (skb_ensure_writable(skb, optoff + 2 + hdr->opt_len))\n\t\tgoto drop;\n\n\t/* Trace pointer may have changed */\n\ttrace = (struct ioam6_trace_hdr *)(skb_network_header(skb)\n\t\t\t\t\t   + optoff + sizeof(*hdr));\n\n\tioam6_fill_trace_data(skb, ns, trace, true);\n\n\tioam6_event(IOAM6_EVENT_TRACE, dev_net(skb->dev),\n\t\t    GFP_ATOMIC, (void *)trace, hdr->opt_len - 2);\n\nIf the skb is cloned or lacks sufficient linear headroom,\nskb_ensure_writable() will invoke pskb_expand_head(), which reallocates\nthe skb's data buffer and frees the old one, invalidating pointers to\nit. While the code recalculates the trace pointer immediately after the\ncall to skb_ensure_writable(), it fails to recalculate the hdr pointer.\n\nThis patch fixes the above by recalculating the hdr pointer before\npassing hdr->opt_len to ioam6_event(), so that we avoid any UaF."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"769723124b7c3b2bfea4cf68ad292698b87c8d01","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"24de676da63c1122d2c13b0d546238b66d1b4e62","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"5af905aa8e91ff8d94572a1e089558f21dcf24ed","versionType":"git"},{"version":"f655c78d6225f585ef60a9d93ffb79d507ff3ad3","status":"affected","lessThan":"e46e6bc97fb1f339730ff1ba74267fbf48e7a422","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/769723124b7c3b2bfea4cf68ad292698b87c8d01"},{"url":"https://git.kernel.org/stable/c/24de676da63c1122d2c13b0d546238b66d1b4e62"},{"url":"https://git.kernel.org/stable/c/5af905aa8e91ff8d94572a1e089558f21dcf24ed"},{"url":"https://git.kernel.org/stable/c/e46e6bc97fb1f339730ff1ba74267fbf48e7a422"}],"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 - The bug is in `ipv6_hop_ioam()`, reached from `ipv6_rcv()` → `ip6_rcv_core()` → `ipv6_parse_hopopts()` → `ip6_parse_tlv()` when processing IPv6 hop-by-hop IOAM options on ingress. A remote attacker can deliver the trigger with a crafted IPv6 packet to any internet-facing or LAN-reachable host/router that has IOAM ingress enabled.\nAC:L - Exploitation requires `skb_ensure_writable()` to reallocate via `pskb_expand_head()`, which occurs when the skb is cloned (e.g., bridge flooding/multicast forwarding sets `skb->cloned` on the original before local delivery to the IP stack). An attacker can reliably create this condition with concurrent traffic/topology choices rather than depending on uncontrollable timing or memory layout.\nPR:N - The attacker needs no privileges on the victim system—only the ability to send IPv6 packets. IOAM namespace/sysctl configuration is a victim-side deployment prerequisite (typical on carrier/ISP telemetry nodes), not a privilege the attacker must hold.\nUI:N - Exploitation is fully attacker-driven by sending a malicious IPv6 packet and requires no action from a victim user.\nS:U - The vulnerability is a kernel heap use-after-free in IPv6 packet processing; successful exploitation would compromise the kernel/host itself, not cross a separate security authority such as a VM guest-to-host or sandbox boundary.\nC:H - After `pskb_expand_head()` frees the old skb buffer, the stale `hdr` pointer is dereferenced for `hdr->opt_len`, constituting a use-after-free read of freed kernel memory; that attacker-influenced length is then used in `ioam6_event_put_trace()`/`nla_put()`, enabling out-of-bounds kernel memory reads and information disclosure.\nI:H - Use-after-free of heap metadata enables memory corruption primitives; the corrupted `opt_len` fed into netlink attribute construction can cause out-of-bounds reads whose contents are attacker-influenced, and UAF bugs in skb handling are classically leveragable toward arbitrary kernel write/code execution.\nA:H - Reading freed memory and passing a corrupted length into `nla_put()` can cause kernel oops/panic (especially with KASAN/overflow checks), and UAF conditions inherently risk system crashes even when full exploitation is not attempted."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:39:34.060Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.12.92"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}