CVE-2026-55564 FreeRDP: Out-of-bounds read in glyph_cache_get via crafted glyph fragments
A malicious RDP server can trigger an out-of-bounds read in FreeRDP clients, potentially disclosing heap data or causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55564?
CVE-2026-55564 is a medium-severity vulnerability in Freerdp Freerdp, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, the glyph_cache_get function in libfreerdp/cache/glyph.c checks whether index is greater than cache->number instead of greater than or equal to it. A malicious RDP server can use GLYPH_FRAGMENT_USE replay in update_process_glyph_fragments to make the default cache receive index 254 when cache->number is 254, reading one pointer beyond the entries array and dereferencing it as a glyph. This can crash the client and may disclose adjacent heap data. This issue is fixed in version 3.27.0.
Which versions are affected by CVE-2026-55564?
It affects 1 product.
Products include Freerdp Freerdp.
How do I fix CVE-2026-55564?
Upgrade to a fixed version.
Is CVE-2026-55564 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55564 exists.
Other vulnerabilities in Freerdp Freerdp
- CVE-2021-37594 Other in n/a
- CVE-2021-37595 Other in n/a
- CVE-2026-67305 FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr
- CVE-2026-66402 FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass
- CVE-2026-67289 FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection
Sources
Also known as DEBIAN-CVE-2026-55564, GHSA-6xmj-pr98-cx4c, UBUNTU-CVE-2026-55564.