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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 access memory outside a lookup table when decoding specially formed Base64 data, particularly on Arm/AArch64 builds. A remote, unauthenticated attacker may affect confidentiality or availability, although exploitation requires high complexity. Upgrade affected deployments promptly.

Executive priority

Treat this as a high-priority patching item, especially for externally reachable or otherwise untrusted-data-facing Arm/AArch64 deployments. The absence of documented active exploitation lowers emergency pressure, but remote unauthenticated reachability and possible confidentiality and availability impact justify timely remediation.

Technical view

Implementation-defined plain-char signedness can weaken a bounds guard in crypto_base64_decode on Arm/AArch64. Bytes from 0x80 through 0xFF may then index beyond a global lookup table. The issue is remotely reachable without privileges or user interaction, has CVSS 3.1 score 7.4, and is fixed in FreeRDP 3.20.1.

Likely exposure

Exposure exists where FreeRDP versions earlier than 3.20.1 process untrusted RDP-related data. Arm/AArch64 builds deserve particular attention because the documented trigger depends on unsigned plain-char behavior. The supplied evidence does not establish exposure for every build, distribution package, or deployment configuration.

Exploitation context

The CVSS vector indicates remote, unauthenticated exploitation without user interaction, but with high attack complexity. The source bundle marks this CVE as absent from KEV and provides no evidence of active exploitation or a public exploit. Potential impact is limited to confidentiality and availability in the supplied scoring.

Researcher notes

CWE mappings include out-of-bounds read, implementation-defined behavior, and out-of-bounds write, but the supplied description specifically documents out-of-bounds table access. It does not establish reliable code execution, affected call paths beyond Base64 decoding, or exploitation in the wild. Architecture and compiler behavior are important validation variables.

Mitigation direction

  • Upgrade FreeRDP to version 3.20.1 or later.
  • Apply the relevant vendor or distribution security update where FreeRDP is packaged.
  • Prioritize exposed Arm/AArch64 systems running affected versions.
  • Consult FreeRDP and distribution advisories for deployment-specific guidance.

Validation and detection

  • Inventory installed and embedded FreeRDP versions across systems and applications.
  • Identify Arm/AArch64 deployments and confirm whether they run versions earlier than 3.20.1.
  • Verify updated systems report FreeRDP 3.20.1 or a vendor-confirmed patched package.
  • Confirm applicable Red Hat errata are installed on affected Red Hat systems.
Prepared
Confidence
high
Sources
5

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.

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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.

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cve · low confidence lookup

CVE-2026-22858 mapping review

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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.

CWE-125 · source CWE mapping

Out-of-bounds Read

Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-758 · source CWE mapping

Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

Reliance on Undefined, Unspecified, or Implementation-Defined Behavior represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-787 · source CWE mapping

Out-of-bounds Write

Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs