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Linux kernel unix_stream_recvmsg slab-memory leak denial of service
CVE-2021-20265 is an uncontrolled resource-consumption vulnerability in the Linux kernel's UNIX-domain stream socket receive path. When a signal is pending during execution of unix_stream_recvmsg, memory resources are improperly freed, resulting in an increasing slab-memory leak. A local unprivileged user can repeatedly trigger the flawed condition until available memory is exhausted, causing the system to crash or become unavailable.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation causes local denial of service by exhausting system memory through slab allocation leakage. The documented impact is availability loss; no confidentiality or integrity impact is stated.
If you can’t patch tonight, do this now.
No suitable standalone mitigation is available. Apply the vendor-supported kernel update and reboot affected hosts.
Patch, then assume compromise.
Install a kernel update containing the upstream fix, then reboot to load the updated kernel. For Red Hat Enterprise Linux 7, fixes were distributed in RHSA-2021:0856 for the standard kernel and RHSA-2021:0857 for kernel-rt. For Red Hat Enterprise Linux 6 Extended Lifecycle Support, the fix was distributed in RHSA-2021:1288. The affected RHEL 7 kernel update is version 3.10.0-1160.21.1.el7; the RHEL 6 ELS update is version 2.6.32-754.39.1.el6.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.