high · CVSS v3 7.1

CVE-2026-98626

CVE-2026-98626 is a high‑severity flaw in the Linux kernel’s BPF CO‑RE relocation handling that allows malformed metadata to poison critical

Overview

CVE-2026-98626 is a high‑severity flaw in the Linux kernel’s BPF CO‑RE relocation handling that allows malformed metadata to poison critical instructions before validation. This can lead to unintended control‑flow changes or data corruption when BPF programs are loaded. The issue was fixed by deferring poisoning until after instruction validation and extending support to ldimm64 halves.

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Restrict CO-RE poisoning to relocatable instructions CO-RE relocation records can name any instruction offset. When a relocation cannot be resolved, bpf_core_patch_insn() currently poisons its target before checking whether that instruction is a valid relocation target. Malformed metadata can therefore replace jumps, calls, exits, register-source arithmetic, or non-immediate loads instead of failing at the relocation step. Handle poisoning only after the instruction has passed the same class and operand-form checks used for a resolved relocation. Route invalid forms through the existing diagnostic and return a hard error. Keep poisoning supported instructions, including both halves of a plain ldimm64, so an unresolved relocation in dead code remains valid. Extend bpf_core_poison_insn() to poison both halves of ldimm64, and return its status directly from each validated instruction case. This avoids routing the success path through a common label and leaves the helper free to report errors. The shared relocation code applies this restriction to both libbpf and in-kernel CO-RE.

Impact

The vulnerability compromises the integrity of BPF programs, potentially allowing attackers to alter jumps, calls, exits, or arithmetic operations. This undermines the confidentiality, integrity, and availability of systems relying on BPF for networking, tracing, or security filtering. Defenders should consider any host running recent kernel versions that use BPF or libbpf as potentially impacted.

Remediation

Apply the latest kernel patch that defers instruction poisoning until after validation, or upgrade to a kernel version that includes the CVE-2026-98626 fix. For systems using libbpf, update to the patched libbpf release. Verify that BPF programs are compiled with the latest compiler flags and that no custom relocation metadata is injected.

Risk context

The CVSS v3 score of 7.1 indicates a high risk, and the absence of EPSS data suggests a moderate but non‑negligible likelihood of exploitation. Defenders should prioritize patching within the next maintenance window.

Affected products

  • Linux kernel
  • libbpf

Scores

Severity
high
CVSS v2
2.1
CVSS v3
7.1
CVSS v4
—
EPSS
—

BPF CO-RE relocation kernel patch

← All CVEs

Related CVEs

high

CVE-2026-98788

In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.

View analysis

high

CVE-2026-98858

In the Linux kernel, the following vulnerability has been resolved: io_uring: fix task_work add use-after-free with SQPOLL For SQPOLL, the sqpoll thread runs task_work off its own list and doesn't need to be told about it, so it can pop and complete a request as soon as mpscq_push() has published it. If that was the last request holding the ring alive, io_ring_exit_work() then frees the ctx, stops the thread, and with it the tctx, while io_req_normal_work_add() is still looking at both after the push: BUG: KASAN: slab-use-after-free in io_req_normal_work_add+0x439/0x510 Read of size 4 at addr ff11000000ca0000 by task repro/55 (...) BUG: KASAN: slab-use-after-free in queue_work_on+0x25/0x70 Write of size 8 at addr ff11000000c3bd00 by task repro/55 Hold an RCU read lock across the add, like io_req_local_work_add() already does, and have io_ring_exit_work() wait for a grace period for SQPOLL rings as well before freeing the ctx.

View analysis

high

CVE-2026-98862

In the Linux kernel, the following vulnerability has been resolved: audit: fix exe mark UAF in kill_rules() kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit tree is pruned. It drops entry->rule.exe before removing the rule from the RCU-visible filter lists. After a rule has been installed with AUDIT_ADD_RULE, which requires CAP_AUDIT_CONTROL, removing the watched directory can race with another task that is still evaluating the rule. In that case, fsnotify can free the executable mark before the reader reaches audit_mark_compare(), causing a use-after-free. KASAN reports: BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0 Unlink the published rules from the RCU-visible lists and retain them on tree->rules for cleanup. If any rule has an executable mark, wait for a single RCU grace period before removing the marks and scheduling the entries for freeing. Otherwise, call_rcu() already provides the required deferred freeing without a synchronous wait.

View analysis

high

CVE-2026-98621

CVE-2026-98621 is a high‑severity Linux kernel vulnerability that allows an attacker to trigger a buffer overflow by sending a GUE packet with an invalid REMCSUM offset. The flaw causes an underflow in the checksum offset handling, leading to a write beyond the destination buffer and potential denial of service or privilege escalation. It can be exploited via crafted network traffic on affected systems.

View analysis