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CVE Record

CVE-2026-22858: FreeRDP has a global-buffer-overflow in crypto_base64_decode

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.20.1, global-buffer-overflow was observed in FreeRDP's Base64 decoding path. The root cause appears to be implementation-defined char signedness: on Arm/AArch64 builds, plain char is treated as unsigned, so the guard c <= 0 can be optimized into a simple c != 0 check. As a result, non-ASCII bytes (e.g., 0x80-0xFF) may bypass the intended range restriction and be used as an index into a global lookup table, causing out-of-bounds access. This vulnerability is fixed in 3.20.1.

HighCVSS 7.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

FreeRDP before 3.20.1 can read outside a global memory table while decoding Base64 data. The issue is tied to platform-specific C behavior, especially Arm/AArch64 builds. Business risk is highest where FreeRDP is exposed to untrusted RDP-related data or embedded in remote access workflows.

Executive priority

Treat as a high-priority patching issue for organizations using FreeRDP in remote access tooling, especially on Arm platforms. No cited evidence shows active exploitation, so urgency is remediation-focused rather than incident-response-driven.

Technical view

The Base64 decoder can use non-ASCII bytes as indexes into a global lookup table because plain char signedness differs by platform. On Arm/AArch64, unsigned char behavior can weaken the intended guard, enabling out-of-bounds access. CVSS 3.1 is 7.4 with network attack vector, high complexity, no privileges, and high confidentiality and availability impact.

Likely exposure

Systems running FreeRDP versions earlier than 3.20.1, including downstream Linux packages and products embedding FreeRDP libraries. Arm/AArch64 builds deserve particular attention based on the reported root cause.

Exploitation context

The source bundle does not cite active exploitation, and KEV is false. The CVSS vector says exploitation is network-reachable, requires high complexity, needs no privileges, and does not require user interaction.

Researcher notes

Evidence supports an implementation-defined signedness bug causing out-of-bounds access in crypto_base64_decode. The bundle lists CWE-125, CWE-758, and CWE-787, but does not provide proof of remote code execution. Avoid assuming exploitability beyond the CVSS impacts and vendor advisory language.

Mitigation direction

  • Upgrade FreeRDP to 3.20.1 or later where upstream packages are used.
  • Apply relevant Red Hat errata for affected supported Red Hat products.
  • Prioritize Arm and AArch64 deployments during remediation planning.
  • Check downstream vendor guidance for embedded or repackaged FreeRDP components.
  • Restrict exposure of remote desktop tooling to trusted networks where practical.

Validation and detection

  • Inventory FreeRDP versions across endpoints, servers, containers, and appliances.
  • Identify applications linking against FreeRDP libraries, not only standalone clients.
  • Confirm whether builds target Arm, AArch64, or other affected architectures.
  • Verify installed package versions against vendor errata and FreeRDP 3.20.1.
  • Review vulnerability scanner results for CVE-2026-22858 and reconcile false negatives.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-125: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-758: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-787: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-22858 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
20Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.4CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H2.25.2redhat-SADP
5.6CVSS 4.0MediumCVSS: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——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

5.6Medium
CVSS 4.0 vector shape for CVE-2026-22858Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: 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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPfreerdp: FreeRDP global-buffer-overflow
other:Red Hat severity ratingcvssV3_1
  • 2026-01-14T18:00:52.497Z: Reported to Red Hat.
  • 2026-01-14T17:56:29.729Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.20.1Listed
Weakness

CWE details

CWE-125CWE-758CWE-787

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.