CVE-2026-31503
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A vulnerability in the Linux kernel's UDP implementation causes wildcard bind conflict checks to be skipped when the hash bucket count exceeds 10. The issue occurs because the code switches to the hash2 table (keyed by address and port) instead of the hash table (keyed by port only), allowing a wildcard bind to succeed despite existing specific-address binds on the same port.
Risk Assessment
An attacker could exploit this to intercept network traffic intended for other services or perform man-in-the-middle attacks by binding a wildcard socket to a port already in use by other processes.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit that moves inet_use_hash2_on_bind() to inet_hashtables.h and applies it in UDP).
Other vulnerabilities in Linux kernel
See all- CVE-2026-80577Unknown
In the Linux kernel's drm/panthor driver, panthor_fw_load_section_entry() skips BO creation for zero-sized firmware sections but adds them to the section list, leading to NULL pointer dereference in later paths. The fix skips adding such sections to the list.
- CVE-2026-80571Unknown
In the Linux kernel powerpc/pseries papr-phy-attest, missing validation of cmd.length could lead to buffer overflow. The fix adds length checks and fixes memory leaks on error paths.
- CVE-2026-80567Unknown
In the Linux kernel Synaptics RMI4 driver (F54), worker errors were not propagated to the V4L2 queue, causing stale or uninitialized data to be delivered to userspace. The fix adds error checking and marks buffers as error state.
- CVE-2026-80566Unknown
In the Linux kernel, the hynitron_cstxxx driver improperly validated touch count and finger IDs. This can lead to corrupted touch state or out-of-bounds buffer access.
- CVE-2026-80564Unknown
In the Linux kernel, the gve driver lacks an implementation of adjfine, leading to a NULL pointer dereference when triggered from userspace, e.g., via testptp.
- CVE-2026-80563Unknown
A use-after-free vulnerability was found in the Linux kernel's gpio-sloppy-logic-analyzer driver. The 'trigger' debugfs file lacked proper protection, allowing a write to freed memory during device unbind. The issue was fixed by using debugfs_create_file() instead of debugfs_create_file_unsafe().
- CVE-2026-80543Unknown
In the Linux kernel, the xcrb_msg_to_type6cprb_msgx() and xcrb_msg_to_type6_ep11cprb_msgx() functions for s390/zcrypt copy a user space message into a kernel buffer based on length, but further processing assumes 4-byte alignment. As a result, up to 3 bytes of uninitialized kernel memory are forwarded to further processing, potentially exposing kernel memory to the crypto card firmware.
- CVE-2026-80542Unknown
In the Linux kernel, the amdgpu driver for AMD Display has a NULL pointer dereference in amdgpu_dm_crtc_set_vblank() when vblank is enabled or queried before a stream is attached to acrtc_state->stream. This can lead to a system crash.
- CVE-2026-80535Unknown
In the Linux kernel XFS filesystem, during directory tree repair, a self-referential directory may be detected. In such a case, the repair code attempts to lock the same inode twice (double iolock/ilock), leading to a deadlock. The fix detects this corner case and handles it appropriately.
- CVE-2026-80533Unknown
In the Linux kernel XFS filesystem, during AGI repair, the function xrep_iunlink_walk_ondisk_bucket may attempt to use the pointer sc->sa.agi_bp, which can be null if the buffer verifier fails. The fix uses ragi->agi_bp instead, which skips verifier checks, to avoid walking off the end of memory.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: udp: Fix wildcard bind conflict check when using hash2 When binding a udp_sock to a local address and port, UDP uses two hashes (udptable->hash and udptable->hash2) for collision detection. The current code switches to "hash2" when hslot->count > 10. "hash2" is keyed by local address and local port. "hash" is keyed by local port only. The issue can be shown in the following bind sequence (pseudo code): bind(fd1, "[fd00::1]:8888") bind(fd2, "[fd00::2]:8888") bind(fd3, "[fd00::3]:8888") bind(fd4, "[fd00::4]:8888") bind(fd5, "[fd00::5]:8888") bind(fd6, "[fd00::6]:8888") bind(fd7, "[fd00::7]:8888") bind(fd8, "[fd00::8]:8888") bind(fd9, "[fd00::9]:8888") bind(fd10, "[fd00::10]:8888") /* Correctly return -EADDRINUSE because "hash" is used * instead of "hash2". udp_lib_lport_inuse() detects the * conflict. */ bind(fail_fd, "[::]:8888") /* After one more socket is bound to "[fd00::11]:8888", * hslot->count exceeds 10 and "hash2" is used instead. */ bind(fd11, "[fd00::11]:8888") bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */ The same issue applies to the IPv4 wildcard address "0.0.0.0" and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For example, if there are existing sockets bound to "192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or "[::ffff:0.0.0.0]:8888" can also miss the conflict when hslot->count > 10. TCP inet_csk_get_port() already has the correct check in inet_use_bhash2_on_bind(). Rename it to inet_use_hash2_on_bind() and move it to inet_hashtables.h so udp.c can reuse it in this fix.

