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CVE-2026-31662

tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in a7db57ccca21f5801609065473c89a38229ecb92; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in 575faea557f1a184a5f09661bd47ebd3ef3769f8; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in a2ea1ef0167d7a84730638d05c20ccdc421b14b6; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in 1b6f13f626665cac67ba5a012765427680518711; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682; From 2f487712b89376fce267223bbb0db93d393d4b09 · fixed in 48a5fe38772b6f039522469ee6131a67838221a8

  • Linux Linux

    4.15

  • KernelLinux

    From 4.15.0 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.169; From 6.2.0 · fixed in 6.6.135; From 6.7.0 · fixed in 6.12.82; From 6.13.0 · fixed in 6.18.23; From 6.19.0 · fixed in 6.19.13

References 8

git.kernel.org