CVE-2026-98773: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: USB: cdc-acm: skip URB restart in port_shutdown if disconnected acm_port_shutdown() is called from the tty-port machinery whenever the last user closes the port. acm_disconnect() sets acm->disconnected and calls tty_port_tty_vhangup(), which eventually triggers port_shutdown(). At that point acm_disconnect() has already called acm_poison_urbs() and is about to free the control and read URBs. However, acm_port_shutdown() unconditionally calls acm_unpoison_urbs() and, when the ALWAYS_POLL_CTRL quirk is set, immediately re-submits the ctrlurb and all read URBs. If the concurrent acm_disconnect() then frees those URBs and their DMA buffers while they are in-flight, the result is a use-after-free in acm_ctrl_irq() or acm_read_bulk_callback() accessing the freed DMA memory. Fix by checking acm->disconnected after draining the delayed anchor and returning early: if we are in a disconnect path the URBs must remain poisoned and must not be resubmitted. The early return is placed after the delayed-anchor drain loop because that loop only cancels write-side accounting (wb->use = false and autopm counter) and does not touch the hardware path.

Metrics

EPSS Probability

0.17%

6.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= d826061aa64cb28089bf4c73e301dd7928662b84, < d97da42e9de577dc827d4e8866e6971deefe2d9c; >= 8fb82e3555a7d56a05d8ef0edee9859f889c0860, < d86775e79838d7d2e38ccf506a7d0f8e2dd4d5d0; >= 603d5a7110832e10165d21f9a1486399457177de, < 9742905d9ed5bf23ebe4c100dec80b6bc50fb522; >= 5d29d7ff8679e5a525f22da467ba33c042e8029b, < a0ed07b5bbb2d8fcef86810453216070691816e7; >= f58752ebcb35e156c85cd1a82d6579c7af3b9023, < 420ca35af891d33522cc08504768ccd60a4c450a; >= f58752ebcb35e156c85cd1a82d6579c7af3b9023, < dc614d6bc991740d41d5a99ac7765c4b675dda88; 283f8162cc3c82086537cbc7dc01870dbeb07a91; f77f10bc76c2da86b4248269472f6d971e37828b; >= 6.1.175, < 6.1.191; >= 6.6.136, < 6.6.160; >= 6.12.83, < 6.12.113; >= 6.18.24, < 6.18.56; >= 6.19.14, < 6.20; >= 7.0.1, < 7.1
Linux	Linux	7.1

References

Timeline

Published: Oct 18, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-98773?

In the Linux kernel, the following vulnerability has been resolved: USB: cdc-acm: skip URB restart in port_shutdown if disconnected acm_port_shutdown() is called from the tty-port machinery whenever the last user closes the port. acm_disconnect() sets acm->disconnected and calls tty_port_tty_vhangup(), which eventually triggers port_shutdown(). At that point acm_disconnect() has already called acm_poison_urbs() and is about to free the control and read URBs. However, acm_port_shutdown() unconditionally calls acm_unpoison_urbs() and, when the ALWAYS_POLL_CTRL quirk is set, immediately re-submits the ctrlurb and all read URBs. If the concurrent acm_disconnect() then frees those URBs and their DMA buffers while they are in-flight, the result is a use-after-free in acm_ctrl_irq() or acm_read_bulk_callback() accessing the freed DMA memory. Fix by checking acm->disconnected after draining the delayed anchor and returning early: if we are in a disconnect path the URBs must remain poisoned and must not be resubmitted. The early return is placed after the delayed-anchor drain loop because that loop only cancels write-side accounting (wb->use = false and autopm counter) and does not touch the hardware path.

How severe is CVE-2026-98773?

Severity scoring for CVE-2026-98773 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-98773?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

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