CVE-2026-55191

HIGHPre-NVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 61% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this weekElevated
8.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.7Exploit: Elevated riskExposed: 0

A fix is available — apply it.

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients that negotiate RDPGFX AVC444 with an H.264 decoder backend calculate the intermediate YUV444 allocation size in libfreerdp/codec/h264.c with 32-bit multiplication in avc444_ensure_buffer. A malicious RDP server can supply surface dimensions for which piDstStride multiplied by padDstHeight wraps to a small nonzero value, causing winpr_aligned_recalloc to allocate an undersized buffer before YUV420CombineToYUV444 writes using the actual stride and rectangle dimensions. This can cause a client crash and may permit code execution through attacker-influenced heap corruption. This issue is fixed in version 3.27.0.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
55(Track*)
EG Risk 55/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity87% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
39%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 19, 2026

Advisory Details (4)

Auto-updated Aug 19, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

3.27.0

Patch available: FreeRDP/FreeRDP 3.27.0

https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0
github_commit

commit 97f40b9e766a (FreeRDP/FreeRDP)

Fix landed in FreeRDP/FreeRDP commit 97f40b9e766a — awaiting tagged release

https://github.com/FreeRDP/FreeRDP/commit/97f40b9e766af375f4e41ac6a3f4397d708d249c
github_pr

Bounds fixes

Fix merged in FreeRDP/FreeRDP PR #12873 on 2026-06-11 — awaiting tagged release

https://github.com/FreeRDP/FreeRDP/pull/12873
github Patch Available🟡 PoC Available

Heap-buffer-overflow write in AVC444 YUV buffer allocation · Advisory · FreeRDP/FreeRDP · GitHub

https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-vx73-w5q6-7jqr

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuwinpr3-utils (3.30.0+dfsg-0ubuntu0.26.04.1) @ resolute2026-08-29ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 21× in last 7d / 39× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 19:25 UTCVendor advisory
  3. 2026-08-29 07:29 UTCEG score recompute
  4. 2026-08-29 07:29 UTCVendor advisory
  5. 2026-08-28 21:41 UTCEPSS rescore
  6. 2026-08-28 19:33 UTCVendor advisory
  7. 2026-08-27 18:44 UTCEG score recompute
  8. 2026-08-27 14:25 UTCEPSS rescore
  9. 2026-08-27 06:45 UTCVendor advisory
  10. 2026-08-26 18:12 UTCEG score recompute
  11. 2026-08-26 18:12 UTCVendor advisory
  12. 2026-08-26 14:46 UTCEPSS rescore
  13. 2026-08-25 18:09 UTCEG score recompute
  14. 2026-08-25 13:49 UTCEPSS rescore
  15. 2026-08-25 06:12 UTCVendor advisory
  16. 2026-08-24 18:18 UTCEG score recompute
  17. 2026-08-24 18:18 UTCVendor advisory
  18. 2026-08-24 06:24 UTCVendor advisory
  19. 2026-08-23 18:29 UTCVendor advisory
  20. 2026-08-23 06:35 UTCEG score recompute
  21. 2026-08-23 06:35 UTCVendor advisory
  22. 2026-08-23 00:19 UTCEPSS rescore
  23. 2026-08-22 18:42 UTCVendor advisory
  24. 2026-08-22 06:48 UTCEG score recompute
  25. 2026-08-22 06:48 UTCVendor advisory
Show 14 more
  1. 2026-08-21 23:49 UTCEPSS rescore
  2. 2026-08-21 18:54 UTCVendor advisory
  3. 2026-08-21 07:00 UTCEG score recompute
  4. 2026-08-21 07:00 UTCVendor advisory
  5. 2026-08-20 22:55 UTCEPSS rescore
  6. 2026-08-20 19:06 UTCVendor advisory
  7. 2026-08-20 07:13 UTCVendor advisory
  8. 2026-08-19 19:19 UTCEG score recompute
  9. 2026-08-19 19:19 UTCVendor advisory
  10. 2026-08-19 18:18 UTCEG score recompute
  11. 2026-08-19 18:18 UTCVendor advisory
  12. 2026-08-19 17:53 UTCEG score recompute
  13. 2026-08-19 17:53 UTCVendor advisory
  14. 2026-08-19 17:52 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-55191?
CVE-2026-55191 is a high vulnerability published on August 19, 2026. FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients that negotiate RDPGFX AVC444 with an H.264 decoder backend calculate the intermediate YUV444 allocation size in libfreerdp/codec/h264.c with 32-bit multiplication in avc444ensurebuffer. A malicious RDP…
When was CVE-2026-55191 disclosed?
CVE-2026-55191 was first published in the National Vulnerability Database on August 19, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55191 actively exploited?
CVE-2026-55191 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 60.6% of all scored CVEs.
What is the CVSS score of CVE-2026-55191?
CVE-2026-55191 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-55191?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55191, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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