high CVSS 7.8 Actively exploited EPSS 0.71%

CVE-2026-53362·Kernel vulnerability

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.

Severity
high
Software
Kernel
Fixed in
7.1.3
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.71% — higher than 52% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-53362 scores 7.8 on CVSS, so a successful attack would be serious — but at 0.71%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.19

Until: 7.1.3

Fixed in: 7.1.3

How to fix this CVE

Update your Linux kernel to version 7.1.3 or later to resolve a memory corruption vulnerability in IPv6 packet fragmentation handling. This flaw affects the paged allocation path when using UDP over IPv6 with MSG_MORE and MSG_SPLICE_PAGES flags, allowing local unprivileged users to write past allocated buffer boundaries. Kernel updates should be applied promptly and followed by a system reboot to activate the patched version.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check current kernel version: uname -r (verify it is not in the 6.19.x–7.1.2 range)
  2. Verify IPv6 stack is loaded: lsmod | grep ipv6 (if present, the vulnerable code path is available)
  3. Monitor for application crashes or memory corruption: dmesg | grep -i 'memory corruption\|segfault\|kernel panic' (look for recent entries suggesting buffer overflow)
  4. Confirm fix applied: After reboot, run uname -r and verify version is 7.1.3 or later

FAQ

What is CVE-2026-53362?

This vulnerability is a memory corruption flaw in the Linux kernel's IPv6 fragmentation logic that incorrectly calculates buffer sizes when handling paginated allocations with the MSG_MORE flag, causing writes beyond allocated memory boundaries.

Is CVE-2026-53362 being actively exploited?

Yes—this vulnerability is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild.

What versions of Kernel are affected by CVE-2026-53362?

Linux kernel versions 6.19 through 7.1.2 are vulnerable; version 7.1.3 and later contain the fix.

How do I check if my server is vulnerable to CVE-2026-53362?

Run uname -r to display your kernel version—if it falls between 6.19.0 and 7.1.2 (inclusive), your system is vulnerable and requires an immediate kernel update.

Does Defensia detect CVE-2026-53362?

Yes—Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2026-53362 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-63795CVSS 10In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error path When p9_client_walk() is called with clone set to false, fid aliases oldfid. If the walk subsequently fails after the request has been sent, the error path jumps to clunk_fid, which currently calls p9_fid_put(fid) unconditionally. This drops a reference to oldfid even though ownership of oldfid remains with the caller. If this is the last reference, oldfid can be clunked and destroyed while the caller still expects it to be valid. A later use or put of oldfid can then trigger a use-after-free or refcount underflow. Fix this by only putting fid in the clunk_fid error path when it does not alias oldfid, matching the existing guard in the error path below. This can be triggered when a multi-component walk is split into multiple p9_client_walk() calls and a later non-cloning walk fails. A reproducer and refcount warning logs are available on request.
CVE-2026-64160CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix potential for tearing in ->remote_i_size and ->zero_point Fix potential tearing in using ->remote_i_size and ->zero_point by copying i_size_read() and i_size_write() and using the same seqcount as for i_size. We need to make sure that netfslib and the filesystems that use it always hold i_lock whilst updating any of the sizes to prevent i_size_seqcount from getting corrupted.
CVE-2026-64125CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: bcmgenet: keep RBUF EEE/PM disabled Setting RBUF_EEE_EN | RBUF_PM_EN in RBUF_ENERGY_CTRL breaks the RX path on GENET hardware once MAC EEE becomes active. RX traffic stops flowing while the link stays up and the usual descriptor/RX error counters remain quiet. In that state the MAC still accepts frames (rbuf_ovflow_cnt keeps climbing) but RBUF no longer forwards them to DMA, so rx_packets is no longer incremented at the netdev level. On some boards the corruption ends up as a paging fault in skb_release_data via bcmgenet_rx_poll on an LPI exit. Reproduced on Pi 4B (BCM2711 + BCM54213PE) and confirmed by Florian Fainelli on an internal Broadcom 4908-family board with the same crash signature. RBUF_PM_EN is not publicly documented. This shows up more often now that phy_support_eee() enables EEE by default, but it also affects older kernels as soon as TX LPI is turned on via ethtool, so it is not specific to recent changes. Always clear RBUF_EEE_EN | RBUF_PM_EN in bcmgenet_eee_enable_set so the bits stay off across resets. UMAC and TBUF setup is left alone so TX-side EEE keeps working.
CVE-2026-64136CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked() Commit 96c4af418586 ("cifs: Fix locking usage for tcon fields") refactored cifs code to change cifs_tcp_ses_lock for tc_lock around tc_count changes. There was missing lock around tc_count increment inside smb2_find_smb_sess_tcon_unlocked().
CVE-2026-53399CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nfsd: release layout stid on setlease failure nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer. The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail. A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work. nfsd4_alloc_layout_stateid() nfs4_alloc_stid() /* idr_alloc_cyclic under cl_lock */ nfsd4_layout_setlease() /* fails */ nfs4_put_stid() nfsd4_free_layout_stateid() delayed_work_pending(&ls->ls_fence_work) /* needs INIT */ nfsd4_close_layout() /* nfsd_file_put(ls->ls_file) */ put_nfs4_file() Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).

References

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