CyberSecBulletin
CVE-2025-21760NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2025-21760 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1, 4d576202b90b1b95a7c428a80b536f91b8201bcc, e24d225e4cb8cf108bde00b76594499b98f0a74d 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 38% chance of exploitation within 30 days, which is in the top 1.42% of all scored CVEs.

Patch this week

EPSS places it among the vulnerabilities most likely to be exploited soon.

What to do

  1. Update Linux to 10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1 or 4d576202b90b1b95a7c428a80b536f91b8201bcc or e24d225e4cb8cf108bde00b76594499b98f0a74d or a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.4.291 or 5.10.235 or 5.15.179 or 6.1.129, 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.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, 10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, 4d576202b90b1b95a7c428a80b536f91b8201bcc; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, e24d225e4cb8cf108bde00b76594499b98f0a74d; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, ae38982f521621c216fc2f5182cd091f4734641d; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, 789230e5a8c1097301afc802e242c79bc8835c67; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, 04e05112f10354ffc3bb6cc796d553bab161594c; 1762f7e88eb34f653b4a915be99a102e347dd45e up to, but not including, ed6ae1f325d3c43966ec1b62ac1459e2b8e45640; and 1 more ranges10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1, 4d576202b90b1b95a7c428a80b536f91b8201bcc, e24d225e4cb8cf108bde00b76594499b98f0a74d, a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d, ae38982f521621c216fc2f5182cd091f4734641d, 789230e5a8c1097301afc802e242c79bc8835c67
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)V3.1.6 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.6 and later; V3.1.7 and laterNot stated
LinuxLinux Kernel2.6.26 up to, but not including, 5.4.291; 5.5 up to, but not including, 5.10.235; 5.11 up to, but not including, 5.15.179; 5.16 up to, but not including, 6.1.129; 6.2 up to, but not including, 6.6.79; 6.7 up to, but not including, 6.12.16; 6.13 up to, but not including, 6.13.4; 6.145.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.79, 6.12.16

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
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:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Scoring systemScoreSeverityScored by
CVSS 3.18.1HighCNA
CVSS 3.17.8HighCISA (ADP)

Official description

In the Linux kernel, the following vulnerability has been resolved: ndisc: extend RCU protection in ndisc_send_skb() ndisc_send_skb() can be called without RTNL or RCU held. Acquire rcu_read_lock() earlier, so that we can use dev_net_rcu() and avoid a potential UAF.

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

References

Recent Use After Free vulnerabilities

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