CVE-2026-53223 Affecting kernel-rt package, versions <0:5.14.0-687.46.1.el9_8


Severity

Recommended
high

Based on AlmaLinux security rating.

Threat Intelligence

EPSS
0.13% (3rd percentile)

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  • Snyk IDSNYK-ALMALINUX9-KERNELRT-19697315
  • published12 Sept 2026
  • disclosed9 Sept 2026

Introduced: 9 Sep 2026

NewCVE-2026-53223  (opens in a new tab)

How to fix?

Upgrade AlmaLinux:9 kernel-rt to version 0:5.14.0-687.46.1.el9_8 or higher.
This issue was patched in ALSA-2026:66180.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt package and not the kernel-rt package as distributed by AlmaLinux. See How to fix? for AlmaLinux:9 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

net: guard timestamp cmsgs to real error queue skbs

skb_is_err_queue() treats PACKET_OUTGOING as the sole marker for an skb from sk_error_queue. That assumption is not true for AF_PACKET sockets: outgoing packet taps are also delivered to packet sockets with skb->pkt_type == PACKET_OUTGOING, but their skb->cb is owned by AF_PACKET instead of struct sock_exterr_skb.

If such an skb is received with timestamping enabled, the generic timestamp cmsg path can read AF_PACKET control-buffer state as sock_exterr_skb::opt_stats. With SO_RXQ_OVFL enabled, the packet drop counter overlaps opt_stats. An odd drop count makes the path emit SCM_TIMESTAMPING_OPT_STATS with skb->len and skb->data. For non-linear skbs this copies past the linear head and can trigger hardened usercopy or disclose adjacent heap contents.

Keep skb_is_err_queue() local to net/socket.c, but make it verify that the PACKET_OUTGOING marker is paired with the sock_rmem_free destructor installed by sock_queue_err_skb(). AF_PACKET receive skbs use normal receive ownership and no longer pass as error-queue skbs, while legitimate sk_error_queue entries keep the PACKET_OUTGOING marker and sock_rmem_free ownership.

CVSS Base Scores

version 3.1