---

name: offensive-krack-fragattacks
description: "KRACK (CVE-2017-13077..082) and FragAttacks (CVE-2020-24586..588 + 26139-26147) — key reinstallation, fragmentation, and aggregation attacks against WPA2 supplicants. Covers Vanhoef's test scripts, viability against modern patched stacks (mostly mitigated post-2021), residual unpatched embedded devices and IoT vendors, and the practical limitations of these attacks in modern engagements. Use when assessing legacy supplicants, embedded clients, or vendors with poor patch cadence."

KRACK & FragAttacks

Two attack families against WPA2 client implementations. Both well-disclosed (KRACK 2017, FragAttacks 2021) and largely patched on modern OSes — but the embedded/IoT long tail keeps them in scope for many engagements.

When These Apply

Family	Target	Patch Status
KRACK	WPA2 supplicants in 4-way handshake / GTK / FT / TDLS	Major OSes patched 2017–2018
FragAttacks	Frame fragmentation/aggregation across WPA2/3	Most stacks patched 2021–2022

Probability of success today is high only against:

• Embedded OEM devices (cameras, sensors, point-of-sale)
• Old Android phones (<8 unpatched)
• Industrial / SCADA Wi-Fi clients
• Wi-Fi-enabled toys, smart bulbs, no-name IoT

Modern Win11 / iOS 16+ / Android 13+ / hostapd-2.10 are mitigated.

KRACK — Key Reinstallation

The 4-way handshake's M3 retransmission causes the supplicant to reinstall the same PTK with reset nonce/replay counters. Frames encrypted under the reused keystream become decryptable.

# Vanhoef's official test scripts
git clone https://github.com/vanhoefm/krackattacks-scripts
cd krackattacks-scripts/krackattack
sudo ./krack-test-client.py --interface wlan0
# Tests the supplicant on a connected client

Output identifies which CVE variants the client is vulnerable to.

Practical Outcomes

When successful:

• Decryption of WPA2-encrypted frames between client and AP
• TKIP downgrade enables packet injection
• Recovery of session keys for the duration of the affected key cycle

Not a PSK recovery — you don't get the wireless password from KRACK.

FragAttacks — Frame Splicing

FragAttacks abuse 802.11 fragmentation and aggregation to inject frames that mix encrypted and plaintext fragments, or to splice attacker-controlled fragments into legitimate frames.

git clone https://github.com/vanhoefm/fragattacks
cd fragattacks
sudo ./test-fragattacks.py wlan0 --interface wlan0
# Suite of ~12 tests covering each variant

CVE	Mechanism
CVE-2020-24588	A-MSDU spoofing — inject crafted A-MSDU subframes
CVE-2020-24587	Mixed-key fragment cache poisoning
CVE-2020-24586	Decoupled fragment cache → reuse
CVE-2020-26139	Forwarding plaintext frames before authentication
CVE-2020-26140	Accepting plaintext frames in protected network

Practical Outcomes

• Inject malicious frames that the client treats as legitimate (HTTP redirect, DNS poison)
• Read decrypted fragments from cached state
• Cross-protect data exfil via crafted A-MSDU

Targeting Workflow

1. Identify the in-scope client (MAC, OS, vendor)
2. Estimate patch likelihood — if modern OS, likely patched; if embedded, likely vulnerable
3. Run the test suite from a controlled AP setup
4. Report each vulnerable variant separately with the matching CVE

# Rogue AP that drives the test
sudo hostapd-mana /tmp/krack_test_ap.conf

# Force client to associate (deauth from real AP, or social-engineer)
sudo aireplay-ng --deauth 5 -a <real-BSSID> -c <client-MAC> wlan0mon

# Run test once associated
sudo ./krack-test-client.py --interface wlan0

Detection

• WIPS may flag deauth-driven roams to attacker AP
• Test scripts generate distinctive frame patterns; modern WIPS recognizes Vanhoef's tooling
• Successful exploitation is essentially silent at protocol level

Reporting

For each vulnerable CVE:

• Client model + firmware version (be specific)
• Variant tested + result (vulnerable / patched / partial)
• Practical impact in the engagement context (decryption only, or injection viable?)
• Remediation: vendor patch URL, mitigation (WPA3 + PMF blocks most)

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Key References

• KRACK: krackattacks.com (Vanhoef)
• FragAttacks: fragattacks.com (Vanhoef)
• Original papers: USENIX Security 2017 (KRACK), USENIX Security 2021 (FragAttacks)
• CISA advisories tracking embedded vendor patches
• Source: https://github.com/SnailSploit/offensive-checklist/blob/main/wireless.md