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Medium

FreeRDP has a global-buffer-overflow in crypto_base64_decode

Type: advisorySources: OSV

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.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-22858
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 20:06 UTC · Revision 1

Source evidence

FreeRDP has a global-buffer-overflow in crypto_base64_decode

core-osv · Original source

Published 14 Jan 2026, 17:56 UTC

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.

osv:CVE-2026-22858
Complete source record
{
  "id": "bc071d75074a6d4728b760a49af31ce5fc4e86badd93938efa4984fe465ff90b",
  "url": "https://osv.dev/vulnerability/CVE-2026-22858",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "FreeRDP has a global-buffer-overflow in crypto_base64_decode",
    "summary": "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.",
    "evidence": "osv:CVE-2026-22858",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-22858",
      "aliases": [
        "CVE-2026-22858",
        "GHSA-qmqf-m84q-x896"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/freerdp/freerdp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7418bc7b7c880a87edade60282f6aeeacd640e47"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.20.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "7418bc7b7c880a87edade60282f6aeeacd640e47"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "3.20.1"
                  },
                  {
                    "cpe": "cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.20.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.5.1",
            "3.5.0",
            "3.4.0",
            "3.3.0",
            "3.2.0",
            "3.1.0",
            "3.0.0",
            "3.0.0-rc0",
            "3.0.0-beta4",
            "3.0.0-beta3",
            "3.0.0-beta2",
            "3.0.0-beta1",
            "2.0.0",
            "2.0.0-rc4",
            "2.0.0-rc3",
            "2.0.0-rc2",
            "2.0.0-rc1",
            "2.0.0-rc0",
            "2.0.0-beta1+android11",
            "2.0.0-beta1+android10",
            "1.2.0-beta1+android9",
            "1.2.0-beta1+android7",
            "1.1.0-beta+2013071101",
            "1.1.0-beta1+ios4",
            "1.1.0-beta1+android5",
            "1.1.0-beta1+android4",
            "1.1.0-beta1+ios3",
            "1.1.0-beta1+ios2",
            "1.1.0-beta1+android3",
            "1.1.0-beta1+android2",
            "1.1.0-beta1+ios1",
            "1.1.0-beta1",
            "1.0.1",
            "1.0.0",
            "1.0-beta5",
            "1.0-beta4",
            "1.0-beta2",
            "1.0-beta1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-22858.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.688027340Z",
      "provider": "osv",
      "references": [
        "https://github.com/FreeRDP/FreeRDP/releases/tag/3.20.1",
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-22858.json",
        "https://access.redhat.com/errata/RHSA-2026:19033",
        "https://access.redhat.com/errata/RHSA-2026:3067",
        "https://access.redhat.com/errata/RHSA-2026:3068",
        "https://access.redhat.com/errata/RHSA-2026:3334",
        "https://access.redhat.com/errata/RHSA-2026:3975",
        "https://access.redhat.com/errata/RHSA-2026:4121",
        "https://access.redhat.com/errata/RHSA-2026:4433",
        "https://access.redhat.com/errata/RHSA-2026:4437",
        "https://access.redhat.com/errata/RHSA-2026:4438",
        "https://access.redhat.com/errata/RHSA-2026:4439",
        "https://access.redhat.com/errata/RHSA-2026:4440",
        "https://access.redhat.com/errata/RHSA-2026:4446",
        "https://access.redhat.com/errata/RHSA-2026:4471",
        "https://access.redhat.com/errata/RHSA-2026:4489",
        "https://access.redhat.com/security/cve/CVE-2026-22858",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/22xxx/CVE-2026-22858.json",
        "https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-qmqf-m84q-x896",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-22858",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2429649"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-125",
          "CWE-758"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/22xxx/CVE-2026-22858.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-22858",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 520286,
  "published_at": "2026-01-14T17:56:29.729+00:00"
}