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CVE-2026-64620· NVD / CVE Program· CNA VulnCheck

FreeRDP before 3.28.0 Heap Buffer Overflow via crypto_rsa_common

FreeRDP before 3.28.0 (affected <=3.27.1) contains a heap-based buffer overflow in crypto_rsa_common() (libfreerdp/crypto/crypto.c). The function writes the modular-exponentiation result into the caller's output buffer via BN_bn2bin() and only afterward checks output_length > out_length, so out-of-bounds bytes are written before the bounds check. On the server side, when a client selects RDP Standard Security, the encrypted client random is decrypted into a fixed 32-byte buffer. Because the server publishes its RSA public key, an unauthenticated attacker can forge a ciphertext whose decrypted value is up to the full modulus length (e.g. 256 bytes for RSA-2048), overflowing the 32-byte heap buffer by up to ~224 attacker-controlled bytes pre-authentication, resulting in denial of service.

CriticalCVSS 9.3 · v4.0—No exploit Fix available

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Published
Jul 20, 2026
Updated
Jul 28, 2026
EPSS
0.9% · 58th percentile
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Report tools

JSON

Action score

37

Monitor

Low priority for now.

CVSS
37 / 40 · 9.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · VulnCheck
9.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
freerdpfreerdp

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • freerdp freerdpbefore 3.28.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (VulnCheck). Independent of NVD's CPE analysis and usually ahead of it.

  • FreeRDP FreeRDP

    • 3.28.0not affected
    • before 3.28.0affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10freerdpbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
AlmaLinux:10freerdp-develbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
AlmaLinux:10freerdp-libsbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
AlmaLinux:10freerdp-serverbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
AlmaLinux:10libwinprbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
AlmaLinux:10libwinpr-develbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
Debian:12freerdp2all versions—
Debian:13freerdp3all versions—
Debian:14freerdp3before 3.28.0+dfsg-13.28.0+dfsg-1
Red Hat:enterprise_linux_eus:10.0freerdpbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-debuginfobefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-debugsourcebefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-develbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-libsbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-libs-debuginfobefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-serverbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0freerdp-server-debuginfobefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0libwinprbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0libwinpr-debuginfobefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux_eus:10.0libwinpr-develbefore 2:3.10.3-3.el10_0.112:3.10.3-3.el10_0.11
Red Hat:enterprise_linux:10.2freerdpbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
Red Hat:enterprise_linux:10.2freerdp-debuginfobefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
Red Hat:enterprise_linux:10.2freerdp-debugsourcebefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8
Red Hat:enterprise_linux:10.2freerdp-develbefore 2:3.10.3-12.el10_2.82:3.10.3-12.el10_2.8

+8

Same product

freerdp: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-8787FreeRDP prior to version 2.0.0-rc4 contains an Integer Overflow that leads to a Heap-Based Buffer Overflow in function gdi_Bitmap_Decompress
    42Plan
  • CVE-2018-8788FreeRDP prior to version 2.0.0-rc4 contains an Out-Of-Bounds Write of up to 4 bytes in function nsc_rle_decode() that results in a memory co
    41Plan
  • CVE-2018-8786FreeRDP prior to version 2.0.0-rc4 contains an Integer Truncation that leads to a Heap-Based Buffer Overflow in function update_read_bitmap_
    41Plan
  • CVE-2018-8785FreeRDP prior to version 2.0.0-rc4 contains a Heap-Based Buffer Overflow in function zgfx_decompress() that results in a memory corruption a
    41Plan
  • CVE-2018-8784FreeRDP prior to version 2.0.0-rc4 contains a Heap-Based Buffer Overflow in function zgfx_decompress_segment() that results in a memory corr
    41Plan
  • CVE-2024-32460FreeRDP Out-Of-Bounds Read in interleaved_decompress
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
FreeRDP FreeRDP3.28.0Vendor (CNA)
almalinux:freerdp2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
almalinux:freerdp-devel2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
almalinux:freerdp-libs2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
almalinux:freerdp-server2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
almalinux:libwinpr2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
almalinux:libwinpr-devel2:3.10.3-12.el10_2.8 · AlmaLinux:10Package registry (OSV)
debian:freerdp33.28.0+dfsg-1 · Debian:14Package registry (OSV)
red hat:freerdp2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-debuginfo2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-debugsource2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-devel2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-libs2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-libs-debuginfo2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-server2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:freerdp-server-debuginfo2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libwinpr2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libwinpr-debuginfo2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libwinpr-devel2:3.10.3-12.el10_2.8 · Red Hat:enterprise_linux:10.2Package registry (OSV)
rocky linux:freerdp2:3.10.3-12.el10_2.8 · Rocky Linux:10Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-31883129 days apartFreeRDP has a `size_t` underflow in ADPCM decoder leads to heap-buffer-overflow write
    39Monitor
  • CVE-2026-6730512 days apartFreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr
    37Monitor
  • CVE-2026-31806129 days apartFreeRDP has a Heap Buffer Overflow in nsc_process_message() via Unchecked SURFACE_BITS_COMMAND Bitmap Dimensions
    37Monitor
  • CVE-2026-4442052 days apartFreeRDP cliprdr server heap-buffer-overflow via undersized capabilitySetLength in CB_CLIP_CAPS
    35Monitor
  • CVE-2026-4442152 days apartFreeRDP RDPGFX CacheToSurface heap-buffer-overflow via clamped-rectangle validation bypass
    35Monitor
  • CVE-2026-5715610 days apartFreeRDP: Integer overflow leading to heap buffer overflow in Orders Delta Points parsing
    34Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records