Linux Kernel up to 7.2.3 svcrdma xdr_count_read_segments allocation of resources

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.2.3 and classified as critical. The affected element is the function xdr_count_read_segments of the component svcrdma. This manipulation causes allocation of resources. This vulnerability is tracked as CVE-2026-89529. The attack is possible to be carried out remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.2.3 and classified as critical. Affected by this vulnerability is the function xdr_count_read_segments of the component svcrdma. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: svcrdma: Reject oversized Read segments at decode time The RPC/RDMA Read list decoder stores wire-supplied segment lengths without validation. xdr_count_read_segments() checks 4-byte alignment for non-zero position values but does not cap the segment length. An oversized rs_length reaches svc_rdma_build_read_segment(), which derives nr_bvec from it and can drive a large dynamic bvec allocation before verifying that enough rq_pages remain. If the post-allocation page-overrun guard fires, the freshly acquired rw context is not returned, leaking the resource. Reject any segment whose length exceeds the receive context's page budget during Read list decoding, consistent with how xdr_check_write_chunk() bounds Write segment counts against rc_maxpages. Also return the rw context on the existing post-allocation overrun path in svc_rdma_build_read_segment(), keeping that defensive guard balanced.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-89529 since 09/11/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/12/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 5120fe54e0e2f5b62797a432115cc61d61117a5b/af6f0e06bed818ee7fc8b869915964410020a1c5 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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