Cloudanix VulnDB

CVE-2026-99056

High · 7.8

CVSS

7.8

EPSS

0.2%

Published

Oct 23, 2026

CISA due date

—

Cloudanix analysis

Next patch cycle SSVC: Track

A recently fixed Linux kernel networking bug could let someone who already has access to a computer crash the system or gain higher privileges, and a working attack has now been published.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
Low
Impact
Full Compromise
Component
OS kernel
Class
Use After Free
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

Race condition during strparser teardown allows in-flight __strp_recv calls (under bh_lock_sock or lock_sock) to access strp->sk after strp_done, resulting in use-after-free.

Why it matters to the business

Local attackers on Linux systems using espintcp can trigger kernel crashes or privilege escalation; the issue is newly exploitable via a public reproducer and affects a widely used kernel component.

How an attack unfolds

An attacker with local access triggers strp_stop concurrently with an in-flight strp_recv (from sk_data_ready or strp_work), causing a use-after-free on strp->sk that the published reproducer converts into arbitrary code execution.

How to fix it

Apply the upstream kernel patch that inserts a dummy lock_sock/release_sock pair in strp_done, switches stopped/paused bits to u8, and ensures no future strp users inherit the race.

How to confirm the fix worked

Inspect strp.c for the lock_sock/release_sock guard around strp_done and confirm stopped/paused fields are declared as u8; test with the published reproducer to verify the crash no longer occurs.

Typical attack path

  1. Obtain local user access on the target Linux system
  2. Force espintcp or strparser teardown while strp_recv is executing
  3. Trigger the race to produce use-after-free
  4. Leverage UAF for privilege escalation or denial of service

How to detect it

Search kernel logs and crash dumps for strparser use-after-free or oops referencing strp->sk; correlate with espintcp teardown events or strp_work activity.

What your security team should do

  • Patch Linux kernels immediately due to public exploit availability
  • Limit local unprivileged access on systems exposing espintcp
  • Monitor kernel logs for strparser-related use-after-free oops
  • Plan removal of the unused general-mode strp code path

The record

In the Linux kernel, the following vulnerability has been resolved: strparser: make sure __strp_recv isn't running before tearing down the parser The comment above strp_done() claims that if strp is stopped, strp_recv will no longer be called. That's only true if the caller has a mechanism (eg locking) to guarantee that strp_recv() calls that started before strp_stop() have completed by the time we call strp_done(). This adds a dummy lock_sock/release_sock pair to guarantee that any in-flight strp_recv() (which runs under either bh_lock_sock or lock_sock, depending if it's called from ->sk_data_ready or strp_work) has completed. Only espintcp can be affected by this race condition, but this patch makes sure no future user of strp can have the bug. This could crash on strp->sk ("general mode" of strp), but this mode has been here for 9 years and has never been used. It'll be gone soon, no point worrying about it. Switch the stopped/paused/etc bits to u8's to avoid races between strp_stop() and strp_pause/unpause(). A reproducer has been published and turns the possible UAF into an exploit [1].

Affected packages

Ecosystem Package Introduced Fixed