Technical impact
FreeRDP, a free Remote Desktop Protocol implementation, contains a division‑by‑zero condition in its MS‑ADPCM and IMA‑ADPCM audio decoders when the block alignment value (nBlockAlign) supplied by the server is zero. The decoder performs a modulus operation with nBlockAlign without validating the value, leading to a SIGFPE that crashes the client. This vulnerability is classified as CWE‑369 and results in a denial‑of‑service condition for users of the affected FreeRDP client.
Affected Systems
Affected systems are installations of the FreeRDP client before version 3.24.0. The issue appears in all builds where the audio codecs are enabled and the server local or remote audio channel (RDPSND) provides an audio format PDU with an nBlockAlign field of zero. End‑users running FreeRDP 3.23.x and earlier are susceptible.
Risk and Exploitability
The CVSS base score is 6.5, indicating moderate severity. The EPSS score is below 1%, suggesting exploitation is currently unlikely in the wild, and the vulnerability is not listed in the CISA KEV catalog. The attack vector requires an attacker who can supply a malformed RDPSND PDU to a FreeRDP client – typically a remote attacker with access to a remote desktop session or control over the server's audio format negotiation. The exploit is straightforward once this condition is met, but the real‑world impact is contained to the client application, causing a crash and loss of availability until the client is restarted or patched.
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