# CVE-2026-98839: vt: selection: Fix unsigned underflow and slab-out-of-bounds read in paste_selection() CVE-2026-98839 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-98839, released October 19, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-98839 - Priority: Routine - CVSS: 3.0 (Low) - EPSS: 0.0017 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Oct 18, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98839 ## Description In the Linux kernel, the following vulnerability has been resolved: vt: selection: Fix unsigned underflow and slab-out-of-bounds read in paste_selection() In paste_selection(), the loop copies min_t(unsigned int, vc_sel.buf_len - pasted,tty->receive_room) bytes per iteration into tty_ldisc_receive_buf() and increments pasted += count. Because the selection mutex (vc_sel.lock) is dropped inside the loop Whenever the line discipline buffer fills up and paste_selection() sleeps on tty->write_wait, a concurrent TIOCLINUX (TIOCL_SETSEL) ioctl can replace vc_sel.buffer with a shorter selection and reduce vc_sel.buf_len below pasted. When paste_selection() resumes, vc_sel.buf_len - pasted underflows as an unsigned integer to a large positive value, causing tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted, NULL, count) to read up to 4094 bytes out-of-bounds past the newly allocated vc_sel.buffer. Fix this by terminating the loop when pasted >= vc_sel.buf_len. Kernel stack trace (Linux 7.3.0-rc3): ================================================================== BUG: KASAN: slab-out-of-bounds in n_tty_receive_buf_common+0xa01/0x1650 Read of size 4094 at addr ffff888101c58010 by task kworker/u17:1/65 Workqueue: events_unbound flush_to_ldisc Call Trace: dump_stack_lvl+0x70/0xa0 print_report+0x153/0x4c6 kasan_report+0xf1/0x120 kasan_check_range+0x11c/0x200 __asan_memcpy+0x29/0x70 n_tty_receive_buf_common+0xa01/0x1650 tty_ldisc_receive_buf+0x66/0x110 tty_port_default_receive_buf+0x6b/0xb0 flush_to_ldisc+0x1b4/0x410 process_one_work+0x6ff/0x1110 worker_thread+0x4a8/0xb70 kthread+0x307/0x3e0 ret_from_fork+0x3ed/0x680 ================================================================== ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel-livepatch-6.18.56-125.164 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | linux Debian 14 | 7.2.10-1 | [DEBIAN-CVE-2026-98839](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98839.md) | Oct 19, 2026 | | Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.56-125.164.amzn2023 | [ALAS2023-2026-3251](https://patchblox.com/security/data/fix/linux/alas2023-2026-3251.md) | Nov 7, 2026 | --- Data as of 2026-11-09T13:31:49Z UTC. 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