CVE-2026-64535: In the Linux kernel, the following vulnerability has been resolved: nvmet-tcp: Fix potential UAF when ddgst mismatch Shivam Kumar found via vulnerab...

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.47%

38.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= fda871c0ba5d2eed2cd1c881573168129da70058, < 96fe2513df590e74b04253a45089cae75569570e; >= fda871c0ba5d2eed2cd1c881573168129da70058, < e091ff83d962f9ed00d9bd70443676de9fe98bdc; >= fda871c0ba5d2eed2cd1c881573168129da70058, < 6f9442983a3e4227afd1c83a5251ddbca585ea21; >= fda871c0ba5d2eed2cd1c881573168129da70058, < 088ee46c18d99baef453afd74181dd40ade044ad; >= fda871c0ba5d2eed2cd1c881573168129da70058, < dbbd07d0a7020b80f6a7028e561908f7b83b3d5a; 91edfca6f8b364d60cde3ddefaf7d03ddf35774b; 4b17476d809273617d3317fa0d4ae78aa488d760; >= 5.10.20, < 5.11; >= 5.11.3, < 5.12
Linux	Linux	5.12

References

Timeline

Published: Jul 27, 2026
Last Modified: Aug 5, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-64535?

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.

How severe is CVE-2026-64535?

CVE-2026-64535 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.47% probability of exploitation in the next 30 days.

How do I fix CVE-2026-64535?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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