CVE-2026-31662

What it is

In the Linux kernel, the following vulnerability has been resolved: tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG The GRP_ACK_MSG handler in tipc_group_proto_rcv() currently decrements bc_ackers on every inbound group ACK, even when the same member has already acknowledged the current broadcast round. Because bc_ackers is a u16, a duplicate ACK received after the last legitimate ACK wraps the counter to 65535. Once wrapped, tipc_group_bc_cong() keeps reporting congestion and later group broadcasts on the affected socket stay blocked until the group is recreated. Fix this by ignoring duplicate or stale ACKs before touching bc_acked or bc_ackers. This makes repeated GRP_ACK_MSG handling idempotent and prevents the underflow path.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-24 15:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-19 19:18 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-04-24 15:16 UTC

Last modified

2026-10-19 19:18 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-191

Record status

Modified

Affected

• Linux Kernel < 5.10.253
• Linux Kernel < 5.15.203
• Linux Kernel < 6.1.169
• Linux Kernel < 6.6.135
• Linux Kernel < 6.12.82
• Linux Kernel < 6.18.23
• Linux Kernel < 6.19.13
• Linux Kernel 4.15

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-31662.md and follow it. Check whether this project is affected by CVE-2026-31662. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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