CVE-2026-64550 in Linux
Summary
by MITRE • 07/28/2026
In the Linux kernel, the following vulnerability has been resolved:
net: qualcomm: rmnet: validate MAP frame length before ingress parsing
When ingress deaggregation is disabled, rmnet_map_ingress_handler() passes the skb straight to __rmnet_map_ingress_handler(), skipping the length validation that rmnet_map_deaggregate() performs on the aggregated path. The parser then dereferences the MAP header and csum header/trailer based on the on-wire pkt_len without checking skb->len, so a short frame is read out of bounds:
BUG: KASAN: slab-out-of-bounds in rmnet_map_checksum_downlink_packet Read of size 1 at addr ffff88801118ed00 by task exploit/147 Call Trace: ... rmnet_map_checksum_downlink_packet (drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c:413) __rmnet_map_ingress_handler (drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c:96) rmnet_rx_handler (drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c:129) __netif_receive_skb_core.constprop.0 (net/core/dev.c:6089) netif_receive_skb (net/core/dev.c:6460) tun_get_user (drivers/net/tun.c:1955) tun_chr_write_iter (drivers/net/tun.c:2001) vfs_write (fs/read_write.c:688) ksys_write (fs/read_write.c:740) do_syscall_64 (arch/x86/entry/syscall_64.c:94) ...
Factor that validation out of rmnet_map_deaggregate() into rmnet_map_validate_packet_len() and run it on the no-aggregation path too. The MAP header is bounds-checked first, since this path can receive a frame shorter than the header.
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Analysis
by VulDB Data Team • 07/28/2026
This vulnerability exists in the Qualcomm rmnet driver within the Linux kernel's network stack, specifically affecting the handling of MAP (Multiplexing and Aggregation Protocol) frames when ingress deaggregation is disabled. The flaw stems from inconsistent validation logic between aggregated and non-aggregated data paths, creating a potential out-of-bounds memory access condition that could lead to system instability or privilege escalation.
The technical implementation involves the rmnet_map_ingress_handler() function which bypasses length validation when deaggregation is disabled, directly passing the socket buffer (skb) to __rmnet_map_ingress_handler() without prior verification of packet boundaries. This contrasts with the normal aggregated path where rmnet_map_deaggregate() performs necessary length checks before processing. The parser then attempts to dereference MAP header and checksum header/trailer fields based on the reported pkt_len value from the wire, but this occurs without verifying that skb->len actually contains sufficient data to satisfy these memory accesses.
When a malformed or short frame is processed through this code path, it triggers a slab-out-of-bounds read operation as demonstrated in the kernel stack trace. The specific function rmnet_map_checksum_downlink_packet at line 413 attempts to read one byte of memory beyond allocated bounds, leading to a KASAN (Kernel Address Sanitizer) detection. This condition manifests when the network driver receives packets that are shorter than expected but still valid from a protocol perspective, causing an out-of-bounds memory access that could be exploited for information disclosure or system compromise.
The vulnerability operates under CWE-129: Improper Validation of Array Index, specifically manifesting as improper validation of packet length before memory access operations. From an ATT&CK perspective, this represents a potential privilege escalation vector through kernel memory corruption (T1068) and could enable code execution in kernel space. The flaw exists in the network driver's ingress handling logic where insufficient bounds checking allows malformed data to proceed through processing paths that assume valid packet boundaries.
The recommended mitigation strategy involves refactoring the validation logic by extracting the length validation functionality from rmnet_map_deaggregate() into a dedicated rmnet_map_validate_packet_len() function. This new validation routine must be invoked on both the aggregated and non-aggregated code paths to ensure consistent bounds checking regardless of deaggregation state. Additionally, the MAP header itself requires initial bounds checking since this path can legitimately receive frames shorter than the full header size, preventing early access violations that would occur before any meaningful data parsing begins.
This remediation approach addresses the fundamental architectural inconsistency in validation logic while maintaining backward compatibility with existing network operations and protocols. The fix ensures that all ingress packet processing paths perform equivalent safety checks before attempting memory dereferences, thereby eliminating the potential for out-of-bounds read conditions that could be leveraged by attackers to gain unauthorized access to kernel memory or cause system crashes through controlled memory corruption patterns.