# CVE-2026-121396: FreeRDP reachable assertion in RTS padding validation

Source: https://junglewise.ai/threats/cve-2026-121396-freerdp-clients-from-3-0-0-before-3-32-2-built-with-verbose  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-03. Updated: 2026-11-03  
License: CC BY 4.0 with a link back

CVE-2026-121396 · Severity: medium · CVSS 4.3 · Published 2026-11-03

FreeRDP is a remote desktop protocol client used to connect to Windows servers and RD Gateways. When connecting through an attacker-controlled RD Gateway, a malformed RPC-over-HTTP packet can trigger an assertion error in debug builds, causing the client to crash and disconnecting the user. This is a denial-of-service attack affecting only clients configured to use a gateway.

Technologies: [FreeRDP](https://junglewise.ai/threats/technologies/freerdp). Vendors: [FreeRDP](https://junglewise.ai/threats/vendors/freerdp).

## Quick answers

**Is CVE-2026-121396 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121396 being exploited in the wild.

**How severe is CVE-2026-121396?** Medium severity, with a CVSS score of 4.3, published 3 November 2026.

**Which products and versions are affected?** FreeRDP 3.0.0 to 3.32.1.

**Is there a fix for CVE-2026-121396?** Yes: fixed in 3.32.2. Until then: Disable verbose WinPR assertions at build time by not setting WITH_VERBOSE_WINPR_ASSERT=ON, or only connect through trusted RD Gateways under your control. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-121396 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-121396?** Check whether you run FreeRDP at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 3.32.2

Disable verbose WinPR assertions at build time by not setting WITH_VERBOSE_WINPR_ASSERT=ON, or only connect through trusted RD Gateways under your control.

## Technical details

The vulnerability is a reachable assertion in the rts_read_auth_verifier function that validates RTS authentication padding. When processing a crafted RTS PDU with inconsistent authentication padding values, the WINPR_ASSERT macro aborts the process on builds compiled with WITH_VERBOSE_WINPR_ASSERT=ON. The attacker must control or intercept the RD Gateway connection; normal release builds with verbose assertions disabled reject the packet cleanly and do not crash.

## Affected products

- FreeRDP FreeRDP 3.0.0 to 3.32.1

## Timeline

- 2026-10-19: disclosed: GitHub security advisory published
- 2026-11-03: advisory: CVE-2026-121396 assigned

## References

- [https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6p3w-fv52-cf24](https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6p3w-fv52-cf24)
- [https://www.vulncheck.com/advisories/freerdp-3.0.0-before-3.32.2-denial-of-service-via-rts-padding-assertion](https://www.vulncheck.com/advisories/freerdp-3.0.0-before-3.32.2-denial-of-service-via-rts-padding-assertion)

## Related threats

- [FreeRDP heap use-after-free in brush cache](https://junglewise.ai/threats/cve-2026-125394-freerdp-before-3-33-0-contains-a-heap-use-after-free)
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- [FreeRDP heap out-of-bounds write in RDPGFX HashTable_GetKeys](https://junglewise.ai/threats/cve-2026-121958-freerdp-through-3-32-1-has-a-heap-out-of-bounds-write-in-the)