CVE-2026-46243

Published Jun 1, 2026

Last updated 17 hours ago

CVSS high 7.1
Linux Kernel
CIFS
SMB Client

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-46243, dubbed "CIFSwitch," is a local privilege escalation vulnerability found in the Linux kernel's Common Internet File System (CIFS) client implementation. The flaw allows an unprivileged local user to forge `cifs.spnego` key descriptions. These descriptions, which typically contain authority-bearing fields like `pid`, `uid`, and `creduid`, are usually treated by the `cifs.upcall` helper as originating from the kernel. However, userspace can also create keys of this type, enabling an attacker to supply these fields without CIFS origin. The vulnerability arises because the kernel's CIFS subsystem fails to verify that `cifs.spnego` key requests originate from the kernel's CIFS client. This allows an unprivileged user to create a forged `cifs.spnego` request, triggering the normal authentication workflow and causing the root-privileged `cifs.upcall` helper to trust attacker-controlled data.

Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: reject userspace cifs.spnego descriptions cifs.spnego key descriptions contain authority-bearing fields such as pid, uid, creduid, and upcall_target that cifs.upcall treats as kernel-originating inputs. However, userspace can also create keys of this type through request_key(2) or add_key(2), allowing those fields to be supplied without CIFS origin. Only accept cifs.spnego descriptions while CIFS is using its private spnego_cred to request the key.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.1
Impact score
5.2
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Severity
HIGH

Weaknesses

nvd@nist.gov
NVD-CWE-noinfo
134c704f-9b21-4f2e-91b3-4a467353bcc0
CWE-20
0b0ca135-0b70-47e7-9f44-1890c2a1c46c
CWE-825

Social media

Hype score
Not currently trending

  1. After analyzing 50% of vulnerabilities from past week, CVE-2026-46243 has 8 articles published from different internet sources, no other cve has these many articles. More information here: https://t.co/SyyDujjO8C #vulnerability #CyberSecurity #ThreatIntel #CVE #SecurityAlert

    @stooee_

    12 Jun 2026

    32 Impressions

    0 Retweets

    0 Likes

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    0 Replies

    0 Quotes

  2. Top 5 Trending CVEs: 1 - CVE-2018-17144 2 - CVE-2026-46243 3 - CVE-2026-49975 4 - CVE-2025-49113 5 - CVE-2026-28318 #cve #cvetrends #cveshield #cybersecurity https://t.co/4Fua3CAN6W

    @CVEShield

    7 Jun 2026

    95 Impressions

    0 Retweets

    0 Likes

    0 Bookmarks

    0 Replies

    0 Quotes

  3. LPE in the Linux kernel's CIFS client implementation CVE: CVE-2026-46243 PT ID: PT-2026-45478 Vendor: Linux Product: Linux CVSS: 7.8 Credits: Asim Viladi Oglu Manizada Description: A privilege escalation vulnerability was found in the Linux kernel's CIFS client implementation.

    @ptdbugs

    6 Jun 2026

    1903 Impressions

    11 Retweets

    22 Likes

    8 Bookmarks

    0 Replies

    0 Quotes

  4. GitHub - MrForkBomb/CIFSwitch-Checker-CVE-2026-46243: Script para comprobar si la vulnerabilidad de Linux CIFSwitch (CVE-2026-46243) nos afecta. Detecta configuraciones potencialmente vulnerables y mitigaciones sin ejecutar exploits. · GitHub https://t.co/UKhKISW2JJ

    @akaclandestine

    2 Jun 2026

    724 Impressions

    0 Retweets

    5 Likes

    2 Bookmarks

    0 Replies

    0 Quotes

Configurations

Related CVEs

  1. In the Linux kernel, the following vulnerability has been resolved: ipv4: account for fraggap on the paged allocation path In __ip_append_data(), when the paged-allocation branch is taken, alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap, but the fraggap bytes carried over from the previous skb are copied into the new skb's linear area at offset transhdrlen by the subsequent skb_copy_and_csum_bits(). The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic.•CVE-2026-53366
  2. In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix zerocopy completion for multi-skb sends When a large message is fragmented into multiple skbs, the zerocopy uarg is only allocated and attached to the last skb in the loop. Non-final skbs carry pinned user pages with no completion tracking, so the kernel has no way to notify userspace when those pages are safe to reuse. If the loop breaks early the uarg is never allocated at all, leaking pinned pages with no completion notification. Fix this by following the approach used by TCP: allocate the zerocopy uarg (if not provided by the caller) before the send loop and attach it to every skb via skb_zcopy_set(), which takes a reference per skb. Each skb's completion properly decrements the refcount, and the notification only fires after the last skb is freed. On failure, if no data was sent, the uarg is cleanly aborted via net_zcopy_put_abort(). This issue was initially discovered by sashiko while reviewing commit 1cb36e252211 ("vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting") but was pre-existing.•CVE-2026-53365
  3. In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_conn: Fix memory leak in hci_le_big_terminate() hci_le_big_terminate() allocates iso_list_data via kzalloc_obj but returns 0 without freeing it when neither pa_sync_term nor big_sync_term flags are set after evaluating the PA and BIG sync connection state. This early-return path was introduced when hci_le_big_terminate() was refactored to take struct hci_conn instead of raw u8 parameters, adding PA/BIG flag evaluation logic. The existing kfree() on hci_cmd_sync_queue failure does not cover this path.•CVE-2026-53364
  4. In the Linux kernel, the following vulnerability has been resolved: xfrm: iptfs: preserve shared-frag marker in iptfs_consume_frags() iptfs_consume_frags() transfers paged fragments from one socket buffer to another but fails to propagate the SKBFL_SHARED_FRAG flag. This is the same class of bug that was fixed in skb_try_coalesce() for CVE-2026-46300: when fragments backed by read-only page-cache pages are merged, the marker indicating their shared nature must be preserved so that ESP can decide correctly whether in-place encryption is safe. Apply the same two-line fix used in skb_try_coalesce() to iptfs_consume_frags().•CVE-2026-53363
  5. In the Linux kernel, the following vulnerability has been resolved: ipv6: account for fraggap on the paged allocation path In __ip6_append_data(), when the paged-allocation branch is taken (MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap (datalen = length + fraggap). When fraggap is non-zero, this is not the first skb and transhdrlen is zero. The fraggap bytes carried over from the previous skb are copied just past the fragment headers in the new skb's linear area. The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount, and the copy writes past skb->end into the trailing skb_shared_info. An unprivileged user can trigger this via a UDPv6 socket using MSG_MORE together with MSG_SPLICE_PAGES. The bad accounting was introduced by commit 773ba4fe9104 ("ipv6: avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix __ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative copy value caused -EINVAL to be returned. That later commit allowed MSG_SPLICE_PAGES to proceed in this case, making the corruption triggerable. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic. Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES case, remove the MSG_SPLICE_PAGES exception from the negative copy check.•CVE-2026-53362

References

Sources include official advisories and independent security research.