CVE-2026-22858Public exploitNetwork attack vector

Client and proxy crash via Base64 table indexing

Published Jan 14, 2026 · Updated Jan 14, 2026

Out-of-bounds read in FreeRDP before 3.20.1 allows remote attackers to crash clients and proxies through crafted Base64 data. In crypto_base64_decode, unsigned plain char values above 0x7f bypass base64_decode_char's nonpositive-value guard and index outside a global lookup table. The path is reached through an RDP server-redirection packet and affects Arm/AArch64 builds whose compiler treats plain char as unsigned.

CVSS severity9.1
Critical
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in FreeRDP before 3.20.1 allows remote attackers to crash clients and proxies through crafted Base64 data. In crypto_base64_decode, unsigned plain char values above 0x7f bypass base64_decode_char's nonpositive-value guard and index outside a global lookup table. The path is reached through an RDP server-redirection packet and affects Arm/AArch64 builds whose compiler treats plain char as unsigned.

The record

CVE
CVE-2026-22858
Published
Jan 14, 2026
Updated
Jan 14, 2026
Vendor
FreeRDP
Product
FreeRDP
Classifications
CWE-758, CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.20.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeRDP · FreeRDPversion=< 3.20.1

Published CVSS scores

5.6GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
7.4Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-758Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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