Vulnerability in Linux kernel (CVE-2025-39758)
Summary
Vulnerability in Linux kernel (CVE-2025-39758). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"),
we have been doing this:
static int siw_tcp_sendpages(struct socket *s, struct page *page, int offset,
size_t size)
[...]
/ Calculate the number of bytes we need to push, for this page
* specifically /
size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);
/ If we can't splice it, then copy it in, as normal /
if (!sendpage_ok(page[i]))
msg.msg_flags &= ~MSG_SPLICE_PAGES;
/ Set the bvec pointing to the page, with len $bytes /
bvec_set_page(&bvec, page[i], bytes, offset);
/ Set the iter to $size, aka the size of the whole sendpages (!!!) /
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
try_page_again:
lock_sock(sk);
/ Sendmsg with $size size (!!!) */
rv = tcp_sendmsg_locked(sk, &msg, size);
This means we've been sending oversized iov_iters and tcp_sendmsg calls
for a while. This has a been a benign bug because sendpage_ok() always
returned true. With the recent slab allocator changes being slowly
introduced into next (that disallow sendpage on large kmalloc
allocations), we have recently hit out-of-bounds crashes, due to slight
differences in iov_iter behavior between the MSG_SPLICE_PAGES and
"regular" copy paths:
(MSG_SP…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2025-39758 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2025-39758" on the vendor's site.
CVE-2025-39758 (Linux kernel) — CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2025-39758 linux-lts Fixed in: 6.12.44-r0
- Debian DEBIAN-CVE-2025-39758 linux Fixed in: 6.12.43-1
- Ubuntu UBUNTU-CVE-2025-39758 linux-hwe-edge
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com