CVE-2026-31662

Description

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.

Is your site exposed to CVE-2026-31662?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-191 CWE-191

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.15.1 — 5.10.253
linux	linux_kernel	5.11 — 5.15.203
linux	linux_kernel	5.16 — 6.1.169
linux	linux_kernel	6.2 — 6.6.135
linux	linux_kernel	6.7 — 6.12.82
linux	linux_kernel	6.13 — 6.18.23
linux	linux_kernel	6.19 — 6.19.13
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711 https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3 https://git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8 https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8 https://git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6 https://git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92 https://git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682

Frequently Asked Questions

What is CVE-2026-31662? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-31662? +

CVE-2026-31662 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-31662? +

CVE-2026-31662 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-31662? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-59368

An integer underflow vulnerability has been identified in Aicloud. An authenticated attacker may trigger this vulnerability by sending a crafted …

CVE-2025-65092

ESF-IDF is the Espressif Internet of Things (IOT) Development Framework. In versions 5.5.1, 5.4.3, and 5.3.4, when the ESP32-P4 uses …

CVE-2026-43916

pam_authnft is a PAM session module binding nftables firewall rules to authenticated sessions via cgroupv2 inodes. Prior to 0.2.0-alpha, a …

CVE-2026-30803

Integer Underflow (Wrap or Wraparound) vulnerability in RTI Connext Micro (Core Libraries) allows Overread Buffers.This issue affects Connext Micro: from …

CVE-2024-0808 9.8

Integer underflow in WebUI in Google Chrome prior to 121.0.6167.85 allowed a remote attacker to potentially exploit heap corruption via …

CVE-2024-23313 9.8

An integer underflow vulnerability exists in the sopen_FAMOS_read functionality of The Biosig Project libbiosig 2.5.0 and Master Branch (ab0ee111). A …