EUVD-2026-66569
GHSA-phcw-98q8-79wf
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector with low privileges via user-namespace CAP_NET_ADMIN; slab OOB enables full memory compromise, justifying C:H/I:H/A:H with no scope change.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
net/sched: cls_u32: skip hash tables in u32_bind_class()
u32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode through the walker callback. u32_bind_class() unconditionally casts the passed fh to tc_u_knode and accesses &n->res, so when fh is actually a tc_u_hnode, which has no tcf_result member, this results in a slab-out-of-bounds read of res->classid in tc_cls_bind_class().
The issue can be reproduced with the following commands:
tc qdisc add dev lo root handle 1: hfsc tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1 tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit
Fix this by skipping hash tables via the TC_U32_KEY(handle) check.
AnalysisAI
Slab-out-of-bounds read in the Linux kernel's cls_u32 traffic classifier allows a local user with networking privileges to corrupt kernel heap memory and escalate to root. The flaw exists in u32_bind_class(), which unconditionally casts all objects enumerated by u32_walk() as tc_u_knode structures, even when the object is a tc_u_hnode (hash table), which lacks the tcf_result member - causing an out-of-bounds access to res->classid. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) local system access, and (2) CAP_NET_ADMIN capability - obtainable without root on systems with unprivileged user namespaces enabled (default on Ubuntu 22.04+, Debian 11+, Fedora, and most Kubernetes node OSes). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-assigned CVSS 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) accurately characterizes this as a high-severity local privilege escalation with low attack complexity. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local attacker with access to user namespaces (available by default on most modern Linux distributions) creates a network namespace to obtain CAP_NET_ADMIN, then issues the exact sequence of tc commands documented in the CVE description: adding an HFSC qdisc, multiple HFSC classes, and a U32 filter. When the second class bind triggers u32_bind_class() to walk the U32 classifier tree, a tc_u_hnode is passed and miscast, causing a slab-out-of-bounds read that can be leveraged for heap layout manipulation and subsequent root privilege escalation. … |
| Remediation | The primary remediation is to upgrade to a patched Linux kernel version: 6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.10, or 7.2+. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Linux systems and determine which run kernel versions prior to 6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.10, or 7.2. …
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Same technique Buffer Overflow
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External POC / Exploit Code
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