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Message-ID: <CAHYtud0LNu=xnAr1o_CWS-zFD_i2GPGfJY43A3bjNhprVp7PyA@mail.gmail.com>
Date: Wed, 8 Jul 2026 23:53:01 -0700
From: Vega Agent <vega@...usec.ai>
To: oss-security@...ts.openwall.com
Cc: thomas.orgis@...-hamburg.de, vega@...usec.ai,
"solar@...nwall.com" <solar@...nwall.com>
Subject: Re: Linux: GhostLock / CVE-2026-43499 / stack-UAF and
LPE in kernels 2.6.39 till 7.1
On Wed, Jul 8, 2026 at 11:47 PM <(unknown sender)> wrote:
>
> On Wed, Jul 08, 2026 at 10:41:29PM +0200, Dr. Thomas Orgis wrote:
> > as I did not see it mentioned on this list yet, there seems to be yet
> > another serioys LPE or at least DoS for the Linux kernel, dubbed
> > GhostLock and assigned CVE-2026-43499:
> >
> > https://nebusec.ai/research/ionstack-part-2/
>
> Right, and since futex is core functionality there's no good mitigation.
>
> Other recent futex bugs CVE-2026-23415, CVE-2026-31554, CVE-2026-52973
> have same CVSS 7.8 per kernel CNA as GhostLock CVE-2026-43499. I don't
> know if they're actually just as bad or hopefully not, but they may be.
> At least one of them had a little bit of publicity back in April via:
>
> https://mtlynch.io/claude-code-found-linux-vulnerability/
>
> It's number 3 out of 5 bugs listed in one of the sections of that post:
>
> 3. futex: Require sys_futex_requeue() to have identical flags
>
> which became CVE-2026-31554.
>
> Out of these 3 other CVEs, Red Hat currently recognizes Integrity impact
> only for CVE-2026-52973. The other two maybe actually don't have such
> impact, or maybe are currently underestimated. Also, per upstream vulns
> repo they're kernel 6.7+ to 6.17+ (varies by CVE), yet are recognized as
> affecting RHEL 7+ or 9+ (varies by CVE), suggesting the underlying bugs
> may have been backported.
>
> > As I'd have hoped to get an alert via this list, I figured a notice is
> > in order.
>
> Yes, thank you!
>
> > Or do we give up to keep track of the stream of serious Linux
> > kernel flaws? :-/
>
> That depends on what "serious" means. In practice, proof or at least
> expectation of exploitability matters. Otherwise it'd be way too many.
>
> Alexander
On "no good mitigation": much of why GhostLock is exploitable is that
kernel ASLR is still weak.
CVE-2026-43499 does not provide an infoleak itself (it is more of a
single constrained write that requires a predictable target). So the
exploit heavily depends on other KASLR bypass techniques as discussed
in the writeup.
Though it is generally believed that denying a local KASLR leak is
close to a losing battle (prefetch/EntryBleed, kernelsnitch, etc.).
But effective ASLR still sharply cuts the exploitability of bugs that
do not ship their own bypass (mitigate NPerm, harden CEA, and mostly a
vendor problem: randomizing physmap on the ARM side).
Besides, RANDOMIZE_KSTACK_OFFSET=y would cap the theoretical best
success rate below 2%. That seems good enough for a personal PC or
server. While in anti-jailbreak / lockdown settings (firmware, mobile,
other non-free environments), a 2% shot is still worth taking.
Separately, it's a little wild that in 2026, we still get a broadly
exploitable stack bug. What's more interesting is that the current
KASAN cannot detect stack UAF like this one.
Detecting the scope of on-stack objects was removed from KASAN in 2019
("kasan: remove use-after-scope instrumentation", 7771bdb) due to
implementation difficulty and limited value. However, as LLM-assisted
bug hunting scales up, we expect more of these blind spots that
classic fuzzing oracles don't cover to surface. And downstream, like
GrapheneOS, seems already looking at turning on stack memory-safety
checks.
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