CVE-2022-49325

In the Linux kernel, the following vulnerability has been resolved:

tcp: add accessors to read/set tp->snd_cwnd

We had various bugs over the years with code breaking the assumption that tp->snd_cwnd is greater than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcp_cwnd_reduction") can trigger, and without a repro we would have to spend considerable time finding the bug.

Instead of complaining too late, we want to catch where and when tp->snd_cwnd is set to an illegal value.

This vulnerability is evaluated as having a Moderate impact because triggering the invalid congestion window state requires specific local conditions or socket manipulations that lead to a kernel warning or denial of service, without enabling code execution or data exposure. While the TCP subsystem is active across standard Red Hat Enterprise Linux installations, the blast radius is confined to localized network instability or system availability degradation. Consequently, the flaw does not pose a direct threat to system confidentiality or integrity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.