CVE-2026-55191

CRITICALNVD 9.89.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.8% (56th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Trending — 3 sources updated this weekElevated
9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.8%CVSS: 9.8Exploit: No code on recordExposed services: Not assessed

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
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
60
EG Risk 60/100

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 (value × EchelonGraph’s weight)
Severity98% × 45%
The EG Score, 9.8 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.8%
EPSS %ILE
56th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 19, 2026

Last Modified

September 22, 2026

Advisory Details (4)

Auto-updated Oct 14, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github.
GitHub advisoryMentions a patch (unverified)🟡 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
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 pull request

Bounds fixes

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

https://github.com/FreeRDP/FreeRDP/pull/12873
GitHub commit

commit 97f40b9e766a (FreeRDP/FreeRDP)

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

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

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuwinpr3-utils (3.30.0+dfsg-0ubuntu0.26.04.1) @ resolute2026-10-08ubuntu

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.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp22.10.0+dfsg1-1 ... 2.11.7+dfsg1-6~deb12u1 (13 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp33.15.0+dfsg-2.1 ... 3.31.1+dfsg-1~bpo13+1 (46 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp33.15.0+dfsg-2.1 ... 3.26.0+dfsg-1~bpo13+1 (33 versions)
  • every version up to 3.27.0+dfsg-1: fixed in 3.27.0+dfsg-1
—

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 15× in last 7d / 130× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 218 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 118 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 01:56 UTCEG score recompute
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  3. 2026-10-12 22:14 UTCEG score recompute
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  5. 2026-10-12 15:56 UTCEG score recompute
  6. 2026-10-11 19:39 UTCEG score recompute
  7. 2026-10-11 16:54 UTCEG score recompute
  8. 2026-10-11 14:17 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  12. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  13. 2026-10-08 07:44 UTCEG score recompute
  14. 2026-10-08 07:44 UTCVendor advisory
  15. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  16. 2026-10-07 10:26 UTCVendor advisory
  17. 2026-10-07 05:20 UTCVendor advisory
  18. 2026-10-07 01:17 UTCVendor advisory
  19. 2026-10-06 21:21 UTCVendor advisory
  20. 2026-10-06 16:58 UTCEG score recompute
  21. 2026-10-06 16:58 UTCVendor advisory
  22. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  23. 2026-10-06 12:26 UTCVendor advisory
  24. 2026-10-06 07:57 UTCVendor advisory
  25. 2026-10-05 17:44 UTCEG score recompute
Show 75 more
  1. 2026-10-05 17:44 UTCVendor advisory
  2. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  3. 2026-10-05 13:53 UTCVendor advisory
  4. 2026-10-05 09:32 UTCVendor advisory
  5. 2026-10-05 05:36 UTCVendor advisory
  6. 2026-10-05 01:45 UTCVendor advisory
  7. 2026-10-04 21:24 UTCVendor advisory
  8. 2026-10-04 14:41 UTCVendor advisory
  9. 2026-10-04 10:23 UTCVendor advisory
  10. 2026-10-04 06:31 UTCVendor advisory
  11. 2026-10-04 02:41 UTCVendor advisory
  12. 2026-10-03 20:48 UTCVendor advisory
  13. 2026-10-03 16:55 UTCEG score recompute
  14. 2026-10-03 16:55 UTCVendor advisory
  15. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  16. 2026-10-03 05:28 UTCVendor advisory
  17. 2026-10-03 01:37 UTCVendor advisory
  18. 2026-10-02 21:36 UTCEG score recompute
  19. 2026-10-02 21:36 UTCVendor advisory
  20. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  21. 2026-10-02 16:48 UTCVendor advisory
  22. 2026-10-02 12:57 UTCVendor advisory
  23. 2026-10-02 07:32 UTCVendor advisory
  24. 2026-10-02 03:41 UTCVendor advisory
  25. 2026-10-01 22:46 UTCEG score recompute
  26. 2026-10-01 22:46 UTCVendor advisory
  27. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  28. 2026-10-01 13:30 UTCVendor advisory
  29. 2026-10-01 09:39 UTCVendor advisory
  30. 2026-10-01 05:43 UTCVendor advisory
  31. 2026-10-01 01:23 UTCVendor advisory
  32. 2026-09-30 20:35 UTCEG score recompute
  33. 2026-09-30 20:35 UTCVendor advisory
  34. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  35. 2026-09-30 08:43 UTCEG score recompute
  36. 2026-09-30 08:43 UTCVendor advisory
  37. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  38. 2026-09-29 05:58 UTCVendor advisory
  39. 2026-09-29 02:07 UTCVendor advisory
  40. 2026-09-28 21:42 UTCEG score recompute
  41. 2026-09-28 21:42 UTCVendor advisory
  42. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  43. 2026-09-28 11:53 UTCVendor advisory
  44. 2026-09-28 07:55 UTCVendor advisory
  45. 2026-09-28 04:03 UTCVendor advisory
  46. 2026-09-28 00:12 UTCVendor advisory
  47. 2026-09-27 20:09 UTCVendor advisory
  48. 2026-09-27 16:09 UTCEG score recompute
  49. 2026-09-27 16:09 UTCVendor advisory
  50. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  51. 2026-09-27 11:00 UTCVendor advisory
  52. 2026-09-27 06:55 UTCEG score recompute
  53. 2026-09-27 06:55 UTCVendor advisory
  54. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  55. 2026-09-25 12:23 UTCVendor advisory
  56. 2026-09-25 08:32 UTCVendor advisory
  57. 2026-09-25 04:42 UTCVendor advisory
  58. 2026-09-25 00:51 UTCVendor advisory
  59. 2026-09-24 19:44 UTCVendor advisory
  60. 2026-09-24 15:42 UTCEG score recompute
  61. 2026-09-24 15:42 UTCVendor advisory
  62. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  63. 2026-09-24 11:40 UTCVendor advisory
  64. 2026-09-24 07:50 UTCVendor advisory
  65. 2026-09-24 03:58 UTCVendor advisory
  66. 2026-09-24 00:05 UTCVendor advisory
  67. 2026-09-23 20:09 UTCEG score recompute
  68. 2026-09-23 20:09 UTCVendor advisory
  69. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  70. 2026-09-23 15:09 UTCVendor advisory
  71. 2026-09-23 11:18 UTCVendor advisory
  72. 2026-09-23 07:27 UTCVendor advisory
  73. 2026-09-23 03:36 UTCVendor advisory
  74. 2026-09-22 23:45 UTCVendor advisory
  75. 2026-09-22 19:55 UTCEG score recompute▲ 1.10

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Frequently asked(5)

What is CVE-2026-55191?
CVE-2026-55191 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55191 published?
The CVE record for CVE-2026-55191 was published on August 19, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 22, 2026; the record at its source may have been updated since.
Is CVE-2026-55191 actively exploited?
CVE-2026-55191 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.8% probability of exploitation in the next 30 days (56th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55191?
CVE-2026-55191 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-55191?
A fix for CVE-2026-55191 is available: update to the fixed version the vendor names in its advisory.

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