CyberSecBulletin
CVE-2026-31662NVD status: Modified

Linux: Integer Underflow (Wrap or Wraparound)

Published Updated By the CyberSecBulletin desk

CVE-2026-31662 is a high-severity integer underflow (wrap or wraparound) vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions a7db57ccca21f5801609065473c89a38229ecb92, 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412, 575faea557f1a184a5f09661bd47ebd3ef3769f8 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.39% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to a7db57ccca21f5801609065473c89a38229ecb92 or 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 or 575faea557f1a184a5f09661bd47ebd3ef3769f8 or 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.169 or 6.6.135, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, a7db57ccca21f5801609065473c89a38229ecb92; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, 575faea557f1a184a5f09661bd47ebd3ef3769f8; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, a2ea1ef0167d7a84730638d05c20ccdc421b14b6; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, 1b6f13f626665cac67ba5a012765427680518711; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682; 2f487712b89376fce267223bbb0db93d393d4b09 up to, but not including, 48a5fe38772b6f039522469ee6131a67838221a8; and 1 more rangesa7db57ccca21f5801609065473c89a38229ecb92, 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412, 575faea557f1a184a5f09661bd47ebd3ef3769f8, 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3, a2ea1ef0167d7a84730638d05c20ccdc421b14b6, 1b6f13f626665cac67ba5a012765427680518711
LinuxLinux Kernel4.15.1 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.169; 6.2 up to, but not including, 6.6.135; 6.7 up to, but not including, 6.12.82; 6.13 up to, but not including, 6.18.23; 6.19 up to, but not including, 6.19.13; 4.15; and 1 more ranges5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, 6.18.23

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Integer Underflow (Wrap or Wraparound)

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

More Integer Underflow (Wrap or Wraparound) vulnerabilities (CWE-191)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Integer Underflow (Wrap or Wraparound) vulnerabilities

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