CVE-2026-23378 in Linux
Summary
by MITRE • 03/25/2026
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_ife: Fix metalist update behavior
Whenever an ife action replace changes the metalist, instead of replacing the old data on the metalist, the current ife code is appending the new metadata. Aside from being innapropriate behavior, this may lead to an unbounded addition of metadata to the metalist which might cause an out of bounds error when running the encode op:
[ 138.423369][ C1] ==================================================================
[ 138.424317][ C1] BUG: KASAN: slab-out-of-bounds in ife_tlv_meta_encode (net/ife/ife.c:168)
[ 138.424906][ C1] Write of size 4 at addr ffff8880077f4ffe by task ife_out_out_bou/255
[ 138.425778][ C1] CPU: 1 UID: 0 PID: 255 Comm: ife_out_out_bou Not tainted 7.0.0-rc1-00169-gfbdfa8da05b6 #624 PREEMPT(full)
[ 138.425795][ C1] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 138.425800][ C1] Call Trace:
[ 138.425804][ C1] <IRQ>
[ 138.425808][ C1] dump_stack_lvl (lib/dump_stack.c:122)
[ 138.425828][ C1] print_report (mm/kasan/report.c:379 mm/kasan/report.c:482)
[ 138.425839][ C1] ? srso_alias_return_thunk (arch/x86/lib/retpoline.S:221)
[ 138.425844][ C1] ? __virt_addr_valid (./arch/x86/include/asm/preempt.h:95 (discriminator 1) ./include/linux/rcupdate.h:975 (discriminator 1) ./include/linux/mmzone.h:2207 (discriminator 1) arch/x86/mm/physaddr.c:54 (discriminator 1))
[ 138.425853][ C1] ? ife_tlv_meta_encode (net/ife/ife.c:168)
[ 138.425859][ C1] kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:597)
[ 138.425868][ C1] ? ife_tlv_meta_encode (net/ife/ife.c:168)
[ 138.425878][ C1] kasan_check_range (mm/kasan/generic.c:186 (discriminator 1) mm/kasan/generic.c:200 (discriminator 1))
[ 138.425884][ C1] __asan_memset (mm/kasan/shadow.c:84 (discriminator 2))
[ 138.425889][ C1] ife_tlv_meta_encode (net/ife/ife.c:168)
[ 138.425893][ C1] ? ife_tlv_meta_encode (net/ife/ife.c:171)
[ 138.425898][ C1] ? srso_alias_return_thunk (arch/x86/lib/retpoline.S:221)
[ 138.425903][ C1] ife_encode_meta_u16 (net/sched/act_ife.c:57)
[ 138.425910][ C1] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114)
[ 138.425916][ C1] ? __asan_memcpy (mm/kasan/shadow.c:105 (discriminator 3))
[ 138.425921][ C1] ? __pfx_ife_encode_meta_u16 (net/sched/act_ife.c:45)
[ 138.425927][ C1] ? srso_alias_return_thunk (arch/x86/lib/retpoline.S:221)
[ 138.425931][ C1] tcf_ife_act (net/sched/act_ife.c:847 net/sched/act_ife.c:879)
To solve this issue, fix the replace behavior by adding the metalist to the ife rcu data structure.
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Analysis
by VulDB Data Team • 05/04/2026
The vulnerability described in CVE-2026-23378 resides within the Linux kernel's networking subsystem, specifically in the ife (if exists) action implementation used for packet classification and modification. This flaw manifests in the net/sched directory where the act_ife module handles packet processing. The issue stems from improper handling of metadata lists when replacing existing ife actions, creating a critical memory management error that can lead to system instability and potential exploitation.
The technical root cause involves the metalist update behavior during ife action replacement operations. When an ife action is replaced, the current implementation incorrectly appends new metadata to the existing metalist instead of properly replacing the old data structure. This erroneous behavior results in unbounded accumulation of metadata entries within the metalist, creating a memory corruption scenario that eventually leads to out-of-bounds memory access. The vulnerability specifically manifests in the ife_tlv_meta_encode function at line 168 of net/ife/ife.c, where a write operation of size 4 occurs at an invalid memory address, triggering a KASAN (Kernel Address Sanitizer) slab-out-of-bounds error.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential pathway for privilege escalation and system compromise. The unbounded addition of metadata entries creates a predictable pattern of memory exhaustion that can be exploited by malicious actors to cause kernel crashes or potentially execute arbitrary code with kernel privileges. According to CWE-129, this vulnerability maps to improper validation of array indices, while the ATT&CK framework would classify this under T1068 (Exploitation for Privilege Escalation) and T1566 (Phishing with Social Engineering) if exploited through network-based attacks. The vulnerability affects systems running Linux kernel versions where the ife action functionality is utilized, particularly in network traffic control scenarios involving complex packet manipulation.
The fix for CVE-2026-23378 requires modifying the replace behavior in the ife RCU (Read-Copy-Update) data structure to properly handle metalist updates instead of appending new metadata entries. This solution ensures that when ife actions are replaced, the existing metalist is correctly overwritten rather than extended, preventing the accumulation of metadata entries that leads to memory corruption. The patch addresses the fundamental flaw in the ife action replacement mechanism by ensuring proper memory management and preventing the unbounded growth of metadata structures that could lead to out-of-bounds memory operations. This remediation aligns with secure coding practices that emphasize proper resource management and bounds checking in kernel-level code, particularly when dealing with dynamic data structures that may be subject to frequent modification operations.