Linux Kernel RDMA/siw: Out-of-bounds write in iWARP header processing
Summary
The siw driver, a software implementation of RDMA over TCP in the Linux kernel, does not limit the copy length correctly when an extended DDP/RDMAP header arrives split across several TCP callbacks. This can overwrite receive state and lead to an out-of-bounds write. The CNA rates the issue 9.8 (critical) with a network vector, no privileges and no user interaction required. It only matters on systems where the siw driver is loaded and reachable over the network.
Affected
- Linux kernel versions with the siw driver, as listed in the CNA and OSV records (for example from 5.10.150 up to the fixed releases below)
- Ranges differ between the CNA and OSV records; check your kernel branch against your distribution's advisory
Fixed in
- 5.10.271
- 5.15.222
- 6.1.189
- 6.6.158
- 6.12.112
- 6.18.54
- 7.2.8
Distribution kernels may use other version numbers. Upstream fix commits are listed in the sources.
Workaround
- Unload the siw module if it is not needed and prevent it from loading (blacklist in modprobe configuration)
- No other workaround known.
Exploitation
No public proof of concept or confirmed exploitation found at the time of writing.
Our recommendation
- Check whether the siw module is loaded (for example with lsmod | grep siw) and whether it is used.
- If it is not needed, unload it and blacklist it.
- If it is needed, update the kernel to a fixed version from your distribution or the stable branch.
- Monitor your distribution's security advisories for updates.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- OSV: CVE-2026-98323 osv.dev
- OSV (Ubuntu): UBUNTU-CVE-2026-98323 osv.dev
- Linux stable commit 262dcd809723723ed8a4e05437ec7e9c21a8f17e git.kernel.org
- Linux stable commit 2c6fbcf4bfac0b2b186acc8d91154c0fa24468a7 git.kernel.org
- Linux stable commit eb4d7a946970469b3ab0c762432bf161d5b0836c git.kernel.org
- SUSE CVE: SUSECVE-CVE-2026-98323 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 21:10.
Original description (NVD)
In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Bound fragmented header copies by the remaining length siw_get_hdr() can receive an extended DDP/RDMAP header across more than one TCP callback. The first callback may receive most of the header, while the next one still limits the copy to hdrlen - MIN_DDP_HDR instead of the number of missing bytes. This makes the destination move past the end of the header and overwrite the receive state, including fpdu_part_rcvd. A later callback can then use a negative fpdu_part_rcvd value as a copy offset, which creates an OOB write. Use the number of header bytes already received when calculating the next copy length.
NVD references (8)
- https://git.kernel.org/stable/c/262dcd809723723ed8a4e05437ec7e9c21a8f17e
- https://git.kernel.org/stable/c/2c6fbcf4bfac0b2b186acc8d91154c0fa24468a7
- https://git.kernel.org/stable/c/8628f8ebf41669302513fb3f0bf0eba38b226742
- https://git.kernel.org/stable/c/9ff797e516dbc1ecb73701ec4c24055712d44411
- https://git.kernel.org/stable/c/af9f5b474a260ad23ffb9793d716a5e3bbce3b48
- https://git.kernel.org/stable/c/b72dcfb9bf1f0f0147cda03dc59e4002a315067f
- https://git.kernel.org/stable/c/e6bdfdf3bcb02d0d626a45e8c98b7e63d2fddf9d
- https://git.kernel.org/stable/c/eb4d7a946970469b3ab0c762432bf161d5b0836c
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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