Service interruption via unclamped route advertised MSS
Published Sep 4, 2026 · Updated Sep 4, 2026
Divide-by-zero in the Linux kernel TCP stack allows attackers to interrupt service through a route-derived zero MSS. tcp_select_initial_window() rounds the receive window with an MSS assumed to be at least one, while TCP consumes unclamped advertised-MSS values from destination metrics. The fault requires an explicit RTAX_ADVMSS below one or a default value reduced to zero by route MTU and min_adv_mss; reaching it triggers a kernel divide-by-zero and can interrupt the host.
Summary
What happened
Divide-by-zero in the Linux kernel TCP stack allows attackers to interrupt service through a route-derived zero MSS. tcp_select_initial_window() rounds the receive window with an MSS assumed to be at least one, while TCP consumes unclamped advertised-MSS values from destination metrics. The fault requires an explicit RTAX_ADVMSS below one or a default value reduced to zero by route MTU and min_adv_mss; reaching it triggers a kernel divide-by-zero and can interrupt the host.
The record
- CVE
- CVE-2026-80847
- Published
- Sep 4, 2026
- Updated
- Sep 4, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- CWE-369, T1499
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 4, 2026CVE publishedPublication date reported by the CVE source.
- Sep 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <31cf2349361902769dc323e4dbf4b449795ec288
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6b8c20bf61924dfc38fefb145c9f7406d73fae53
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1
- Affected versionversion=2.6.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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