CVE-2026-31883
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, a size_t underflow in the IMA-ADPCM and MS-ADPCM audio decoders leads to heap-buffer-overflow write via the RDPSND audio channel. In libfreerdp/codec/dsp.c, the IMA-ADPCM and MS-ADPCM decoders subtract block header sizes from a size_t variable without checking for underflow. When nBlockAlign (received from the server) is set such that size % block_size == 0 triggers the header parsing at a point where size is smaller than the header (4 or 8 bytes), the subtraction wraps size to ~SIZE_MAX. The while (size > 0) loop then continues for an astronomical number of iterations. This vulnerability is fixed in 3.24.0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFreeRDP versions before 3.24.0 contain a size_t underflow vulnerability in the IMA-ADPCM and MS-ADPCM audio decoders in libfreerdp/codec/dsp.c. When processing RDPSND audio channel data, the decoders subtract block header sizes (4 or 8 bytes) from a size_t variable without validating that size is large enough. When nBlockAlign from the server causes size to be smaller than the header, the subtraction wraps to ~SIZE_MAX, causing the while (size > 0) loop to iterate astronomically and trigger heap-buffer-overflow writes.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 3.24.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine FreeRDP installed versionRun `freerdp-version` or check your package manager (dpkg -l freerdp, rpm -qa freerdp, brew list freerdp)Affected if Version is present and less than 3.24.0
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Check for libfreerdp codec libraryLocate libfreerdp/codec/dsp.c or the compiled library containing the ADPCM decoders (typically in /usr/lib/ or /usr/local/lib/)Affected if The DSP codec library exists and predates the 3.24.0 release
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Identify RDP audio channel configurationExamine FreeRDP connection configurations or command-line arguments for audio redirection settings (--rdpsnd, -r sound: or similar audio flags)Affected if RDP audio (RDPSND) channel is enabled or configured for the connection
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Verify audio codec in useIf RDP audio is active, inspect server-supplied nBlockAlign parameter in RDPSND PDUs during audio negotiationAffected if Server sends a nBlockAlign value smaller than 4 bytes for IMA-ADPCM or 8 bytes for MS-ADPCM, triggering the underflow condition
You are affected if FreeRDP version is below 3.24.0 AND RDP audio channel processing is enabled and receives malformed nBlockAlign from a malicious or compromised RDP server.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped3.24.0
Upgrade FreeRDP to version 3.24.0 or later which contains the fix for this underflow vulnerability. If immediate upgrade is not possible, consider disabling or restricting RDP audio channel processing as a compensating control.
FreeRDP 3.24.0
- Check current FreeRDP version (e.g., via package manager, `freerdp-version`, or library version check)
- Upgrade FreeRDP to version 3.24.0 or later using the appropriate package manager or build system
- Verify the upgrade was successful by checking the installed version
- If building from source, ensure the commit 16df2300e1e3f5a51f68fb1626429e58b531b7c8 or version 3.24.0 is included
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-31883 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-31883 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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