FreeRDP before 3.32.2 Heap Buffer Overflow via rpc_client_recv_fragment
Only FreeRDP clients before 3.32.2 that fall back to the RD Gateway TSG/RPC path are affected, and only when the gateway is malicious or compromised. The fix is in 3.32.2.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- Proof of concept public, per CISA
- Fix
- Fixed in 3.32.2
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 3.32.2.
- Exploitation15/40CISA rates a proof of concept as public
- Exposure20/25No login or user action needed, CISA rates it automatable · Data gap: Advisories don't say whether default setups are affected
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 74 if added to CISA KEV
- Would score about 69 if CISA's SSVC rates exploitation active
- Would score about 49 if advisories confirm default setups are exposed
CVE-2026-121964 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects FreeRDP; fixed in 3.32.2.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 44/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Fix
- Fixed in 3.32.2
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: yes
- Technical impact: partial
Summary
FreeRDP's RD Gateway RPC client has a heap-based buffer overflow that an attacker can trigger remotely, without logging in and without any user action, by sending crafted RPC fragments from a malicious or compromised RD Gateway. Successful exploitation can overwrite client heap memory, causing a crash or potentially arbitrary code execution.
Read the original description
FreeRDP before 3.32.2 contains a heap-based buffer overflow in the RD Gateway RPC client, where rpc_client_recv_fragment writes BIND_ACK and ALTER_CONTEXT_RESP fragments into a persistent PDU stream after checking only total capacity rather than remaining capacity from the current stream position. A malicious or compromised RD Gateway can send crafted RPC fragments with manipulated alloc_hint and frag_length values to overwrite client heap memory with attacker-controlled data, causing a crash or potentially arbitrary code execution.
What to do
Upgrade to a fixed version: 3.32.2.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: poc · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- FreeRDP FreeRDP
fixed in 3.32.2
Evidence 2
- Advisory
- Link
Corrections
None so far.
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Questions about CVE-2026-121964
Is CVE-2026-121964 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A heap buffer overflow in FreeRDP's RPC fragment receive code lets the gateway write out of bounds in the client's memory, with the length and content chosen by the gateway. This can crash the client and may potentially lead to arbitrary code execution.Source: github.com, vulncheck.com
Which versions are affected by CVE-2026-121964?
FreeRDP: before 3.32.2.Source: cve.now feed data
Am I affected, and how do I check?
FreeRDP versions before 3.32.2 are affected, but only in the RD Gateway TSG/RPC path, which the client uses when the RD Gateway HTTP and WebSocket paths fail, and only when the gateway is malicious or compromised and completes TLS and NLA negotiation. To check, compare the installed FreeRDP version against 3.32.2 and see whether connections go through an RD Gateway that falls back to TSG.Source: github.com, vulncheck.com
How do I fix CVE-2026-121964?
Upgrade FreeRDP to 3.32.2 or later. The facts give no workaround.Source: github.com, vulncheck.com