EUVD-2026-76466
GHSA-6h6h-gvhm-2hwq
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
MPLS forwarding implies adjacent vector; specific nonlinear-skb layout makes AC:H; no auth (PR:N); narrow freed-memory read gives C:L, crash gives A:H, no integrity impact.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
mpls: reload header after pskb_may_pull()
mpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop when an MPLS route has multiple nexthops. While walking the MPLS label stack, the hash routine caches hdr for the current label. After finding the bottom-of-stack label, it calls pskb_may_pull() before reading the inner IP header.
If an skb is constructed with the inner IP header in nonlinear data and insufficient tailroom in the linear head, pskb_may_pull() calls pskb_expand_head() to replace the skb head and free the old one. This leaves hdr pointing to freed memory. The IPv6 path can invalidate hdr again when it performs a second pull for the larger header.
The issue was found through static analysis. A reproducer sending a legal Geneve packet through a bareudp/MPLS multipath setup triggered the same KASAN report in 2 of 2 unpatched runs:
BUG: KASAN: slab-use-after-free in mpls_select_multipath Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23
Call Trace: mpls_select_multipath mpls_forward __netif_receive_skb_list_core netif_receive_skb_list_internal napi_complete_done gro_cell_poll __napi_poll net_rx_action
Freed by task 23: kfree pskb_expand_head __pskb_pull_tail mpls_select_multipath
Reload hdr from the current skb head after each successful pull before deriving the inner IPv4 or IPv6 header pointer.
AnalysisAI
Use-after-free in the Linux kernel MPLS forwarding path allows a crafted packet to trigger a slab read of freed memory during multipath nexthop selection. mpls_select_multipath()/mpls_multipath_hash() cache a header pointer, then call pskb_may_pull(), which can invoke pskb_expand_head() and free the old skb head - leaving the cached pointer dangling and read afterward. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the target host to be forwarding MPLS traffic with a route configured for multiple nexthops (MPLS multipath/ECMP), so that mpls_select_multipath()/mpls_multipath_hash() runs. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The input CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H = 9.8) substantially overstates real-world risk. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: upgrade to Linux 6.12.109, 6.18.50, 7.2.4, or 7.3-rc1 (or your distribution's kernel carrying the backported fix that reloads hdr from the current skb head after each successful pskb_may_pull()). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems running Linux with MPLS multipath forwarding enabled, with priority on carrier-grade and production network infrastructure. …
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