Vulnerability in linux (DEBIAN-CVE-2026-72139)

Summary

Vulnerability in linux (DEBIAN-CVE-2026-72139). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 7.1.5-1 or later.

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved: tcp: defer md5sig_info kfree past RCU grace period in tcp_connect The md5+ao reconciliation in tcp_connect() (net/ipv4/tcp_output.c) has two symmetric branches: if (needs_md5) { tcp_ao_destroy_sock(sk, false); } else if (needs_ao) { tcp_clear_md5_list(sk); kfree(rcu_replace_pointer(tp->md5sig_info, NULL, ...)); } Both branches free a per-socket auth-info object while the socket is in TCP_SYN_SENT and is already on the inet ehash (inserted by inet_hash_connect() in tcp_v4_connect()). Both branches are reachable by softirq RX-path readers that load the corresponding info pointer via implicit RCU before bh_lock_sock_nested() is taken. The needs_md5 branch is fixed in the prior patch by re-introducing the call_rcu() free in tcp_ao_destroy_sock(): the equivalent per-key loop runs inside tcp_ao_info_free_rcu(), the RCU callback, so by the time it frees each tcp_ao_key all softirq readers that captured the container have already completed rcu_read_unlock(). The needs_ao branch is not symmetric in the same way. The container free can be deferred via kfree_rcu(md5sig, rcu) -- struct tcp_md5sig_info already has the required rcu member (include/net/tcp.h:1999-2002), and the rest of the tree already does this in the tcp_md5sig_info_add() rollback paths (net/ipv4/tcp_ipv4.c:1410, 1436). But the per-key teardown is done by tcp_clear_md5_list() in process context BEFORE the container's RCU grace period: it wa…

Source: OSV.dev (Open Source Vulnerabilities) OSV

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 DEBIAN-CVE-2026-72139 has been found in linux.
Successful exploitation can lead to full system takeover.
What to do: upgrade linux to 7.1.5-1 or later.
If unsure, ask your IT team or search "linux DEBIAN-CVE-2026-72139" on the vendor's site.

DEBIAN-CVE-2026-72139 (linux)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 7.1.5-1 — apply immediately
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.

❓ What is the problem

A vulnerability (unclassified) exists in linux.

📍 Affected scope

Check the vendor advisory for the affected versions of linux.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 7.1.5-1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'linux' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'linux' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で linux を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade linux to 7.1.5-1
```
ステージング環境で 7.1.5-1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-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

Debian:14 linux

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.1.5-1"}]}]

References

advisory security-tracker.debian.org