CyberSecBulletin
CVE-2026-43203NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-43203 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 91f25749aaf57c47ae1e12478144e6ea8c8562f2, 73fbc5d1a9ccb626937500bbd67136f077d8237b, aba0b4bc09376dfc3d53c826514fe38fc8337f52 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 91f25749aaf57c47ae1e12478144e6ea8c8562f2 or 73fbc5d1a9ccb626937500bbd67136f077d8237b or aba0b4bc09376dfc3d53c826514fe38fc8337f52 or e075ec9b08f862dade8011481058f7eb5f716c57, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.252 or 5.15.202 or 6.1.165 or 6.6.128, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  4. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 91f25749aaf57c47ae1e12478144e6ea8c8562f2; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 73fbc5d1a9ccb626937500bbd67136f077d8237b; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, aba0b4bc09376dfc3d53c826514fe38fc8337f52; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, e075ec9b08f862dade8011481058f7eb5f716c57; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 97900f512252a59f23d6ce4ab215cc88fed66e68; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, e4ff4e3ffcf9d5aad380cdd1d8cdc008bb34f97d; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 5189368f10903956be05062d160b2804bf5e5016; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 8930878101cd40063888a68af73b1b0f8b6c79bc; and 1 more ranges91f25749aaf57c47ae1e12478144e6ea8c8562f2, 73fbc5d1a9ccb626937500bbd67136f077d8237b, aba0b4bc09376dfc3d53c826514fe38fc8337f52, e075ec9b08f862dade8011481058f7eb5f716c57, 97900f512252a59f23d6ce4ab215cc88fed66e68, e4ff4e3ffcf9d5aad380cdd1d8cdc008bb34f97d
LinuxLinux Kernel2.6.12.1 up to, but not including, 5.10.252; 5.11 up to, but not including, 5.15.202; 5.16 up to, but not including, 6.1.165; 6.2 up to, but not including, 6.6.128; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.6; 2.6.125.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: atm: fore200e: fix use-after-free in tasklets during device removal When the PCA-200E or SBA-200E adapter is being detached, the fore200e is deallocated. However, the tx_tasklet or rx_tasklet may still be running or pending, leading to use-after-free bug when the already freed fore200e is accessed again in fore200e_tx_tasklet() or fore200e_rx_tasklet(). One of the race conditions can occur as follows: CPU 0 (cleanup) | CPU 1 (tasklet) fore200e_pca_remove_one() | fore200e_interrupt() fore200e_shutdown() | tasklet_schedule() kfree(fore200e) | fore200e_tx_tasklet() | fore200e-> // UAF Fix this by ensuring tx_tasklet or rx_tasklet is properly canceled before the fore200e is released. Add tasklet_kill() in fore200e_shutdown() to synchronize with any pending or running tasklets. Moreover, since fore200e_reset() could prevent further interrupts or data transfers, the tasklet_kill() should be placed after fore200e_reset() to prevent the tasklet from being rescheduled in fore200e_interrupt(). Finally, it only needs to do tasklet_kill() when the fore200e state is greater than or equal to FORE200E_STATE_IRQ, since tasklets are uninitialized in earlier states. In a word, the tasklet_kill() should be placed in the FORE200E_STATE_IRQ branch within the switch...case structure. This bug was identified through static analysis.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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