CyberSecBulletin
CVE-2026-45920NVD status: Undergoing Analysis

Linux: Double Free

Published Updated By the CyberSecBulletin desk

CVE-2026-45920 is a high-severity double free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 523d5a4df3c649fa305c89efb552ec62a1ce9d3d, ca408af08544d96769c93a3d81a7f63f61129e95, 55576fa14771d33994c29a9ae960e07bb3f56c20 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 0.15% 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 523d5a4df3c649fa305c89efb552ec62a1ce9d3d or ca408af08544d96769c93a3d81a7f63f61129e95 or 55576fa14771d33994c29a9ae960e07bb3f56c20 or dbc4e10619ed87a50e637b96f2e574df36a7a769, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.167 or 6.6.130, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 523d5a4df3c649fa305c89efb552ec62a1ce9d3d; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, ca408af08544d96769c93a3d81a7f63f61129e95; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 55576fa14771d33994c29a9ae960e07bb3f56c20; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, dbc4e10619ed87a50e637b96f2e574df36a7a769; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 61e372122b6d95aec940fdaea0a16f988f359897; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 3924aea2c33df3864929c1acd178bfc29d8f005f; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 81982a11406c5da6c6e2b188028e7056e16b7128; 0087d9fb3f29f59e8d42c8b058376d80e5adde4c up to, but not including, 94a8cea54cd935c54fa2fba70354757c0fc245e3; and 1 more ranges523d5a4df3c649fa305c89efb552ec62a1ce9d3d, ca408af08544d96769c93a3d81a7f63f61129e95, 55576fa14771d33994c29a9ae960e07bb3f56c20, dbc4e10619ed87a50e637b96f2e574df36a7a769, 61e372122b6d95aec940fdaea0a16f988f359897, 3924aea2c33df3864929c1acd178bfc29d8f005f
LinuxLinux Kernel2.6.29 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.14; 6.19 up to, but not including, 6.19.45.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.75, 6.18.14

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
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix dirtyclusters double decrement on fs shutdown fstests test generic/388 occasionally reproduces a warning in ext4_put_super() associated with the dirty clusters count: WARNING: CPU: 7 PID: 76064 at fs/ext4/super.c:1324 ext4_put_super+0x48c/0x590 [ext4] Tracing the failure shows that the warning fires due to an s_dirtyclusters_counter value of -1. IOW, this appears to be a spurious decrement as opposed to some sort of leak. Further tracing of the dirty cluster count deltas and an LLM scan of the resulting output identified the cause as a double decrement in the error path between ext4_mb_mark_diskspace_used() and the caller ext4_mb_new_blocks(). First, note that generic/388 is a shutdown vs. fsstress test and so produces a random set of operations and shutdown injections. In the problematic case, the shutdown triggers an error return from the ext4_handle_dirty_metadata() call(s) made from ext4_mb_mark_context(). The changed value is non-zero at this point, so ext4_mb_mark_diskspace_used() does not exit after the error bubbles up from ext4_mb_mark_context(). Instead, the former decrements both cluster counters and returns the error up to ext4_mb_new_blocks(). The latter falls into the !ar->len out path which decrements the dirty clusters counter a second time, creating the inconsistency. To avoid this problem and simplify ownership of the cluster reservation in this codepath, lift the counter reduction to a single place in the caller. This makes it more clear that ext4_mb_new_blocks() is responsible for acquiring cluster reservation (via ext4_claim_free_clusters()) in the !delalloc case as well as releasing it, regardless of whether it ends up consumed or returned due to failure.

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

The underlying weakness: Double Free

The product calls free() twice on the same memory address.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
  • Use a static analysis tool to find double free instances.

More Double Free vulnerabilities (CWE-415)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Double Free vulnerabilities

Spotted an error? Tell us.