{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-98550 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-98550 is a high-severity vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-98550 and fix it if it is affected.\n\nWhat it is: CVE-2026-98550 is a high-severity vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-98550 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-98550/ (Markdown: https://insights.sbomify.com/CVE-2026-98550/index.md)","id":"CVE-2026-98550","markdown":"https://insights.sbomify.com/CVE-2026-98550/index.md","name":"CVE-2026-98550","record":{"aliases":["AZL-109167","BELL-CVE-2026-98550","DEBIAN-CVE-2026-98550","GHSA-xqp5-j42w-5fq8","UBUNTU-CVE-2026-98550"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Linux kernel TIPC","requires_auth":"none","summary":"An attacker can cause a denial of service in the Linux kernel TIPC module by sending invalid group acknowledgment messages that trigger an integer underflow.","user_interaction":"not_required","vuln_class":"integer_overflow"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":7.5,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow\n\nCommit 48a5fe38772b (\"tipc: fix bc_ackers underflow on duplicate\nGRP_ACK_MSG\") rejected duplicate/stale ACKs in tipc_group_proto_rcv()\nby returning early when less_eq(acked, m-\u003ebc_acked).\n\nHowever, that check remains incomplete in two ways:\n\n1. When grp-\u003ebc_ackers is zero (e.g. on a quiet group, when replicast\n   ACKs were not requested, or after all expected members have already\n   acknowledged), an unexpected GRP_ACK_MSG with acked \u003e m-\u003ebc_acked\n   passes less_eq() and unconditionally decrements grp-\u003ebc_ackers.\n   Because bc_ackers is a u16, this wraps to 65535, causing\n   tipc_group_bc_cong() to permanently report congestion and blocking\n   all future group broadcasts on the socket.\n\n2. During an active broadcast round (grp-\u003ebc_ackers \u003e 0), the sender\n   transmits packet S and advances grp-\u003ebc_snd_nxt to S + 1. Receivers\n   increment their expected counter to S + 1 upon consuming packet S,\n   so the only valid ACK value for the current round is strictly\n   acked == grp-\u003ebc_snd_nxt.\n\n   However, tipc_group_update_bc_members() initializes each member's\n   m-\u003ebc_acked to prev = grp-\u003ebc_snd_nxt - 1 (S - 1 before increment).\n   This leaves a 2-sequence gap (S - 1 to S + 1) in sequence space.\n   An incoming ACK is therefore neither rejected as duplicate nor\n   prevented from decrementing grp-\u003ebc_ackers if an unexpected or stale\n   value (such as S) is received. A member sending acked = S followed\n   by acked = S + 1 could decrement grp-\u003ebc_ackers twice in the same\n   round, prematurely clearing bc_ackers or underflowing it.\n\nFix this by:\n- Dropping GRP_ACK_MSG immediately if grp-\u003ebc_ackers is zero.\n- Requiring acked == grp-\u003ebc_snd_nxt and rejecting duplicates where\n  m-\u003ebc_acked == acked. Because replicast broadcast rounds are strictly\n  sequential, only grp-\u003ebc_snd_nxt can be acknowledged, and each member\n  can acknowledge at most once per round.\n\nNote that a related pre-existing issue in tipc_group_delete_member()\n(where grp-\u003ebc_ackers decrementing to zero upon member departure does\nnot restore *grp-\u003eopen or trigger a socket wakeup) will be addressed\nin a separate patch.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"tipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow","id":"CVE-2026-98550","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"integer_overflow","year":"2026"},"n_packages":0,"n_references":8,"next":{"headline":"perf/core: Fill branch entries with a single assignment","id":"CVE-2026-98551"},"packages":[],"prev":{"headline":"tcp: prevent collapsing skbs across boundary in rtx queue","id":"CVE-2026-98549"},"products":["Linux"],"published":"2026-10-18","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-10-24","vendors":["Linux"]},"summary":"An attacker can cause a denial of service in the Linux kernel TIPC module by sending invalid group acknowledgment messages that trigger an integer underflow.","url":"https://insights.sbomify.com/CVE-2026-98550/"}