CVE-2026-55121

MEDIUMPre-NVD 5.55.5
EchelonGraph scoreMEDIUM confidence

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

Score 5.5 from GitHub Security Advisory published 2026-07-14. The CNA's CVSS baseline 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: the CNA's CVSS, EPSS, GitHub Security Advisory
Trending — 4 sources updated this week
5.5EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.

CVSS v3
5.5
EG Score
5.5MEDIUMmedium confidence
EG Risk
25
EG Risk 25/100

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)
Severity55% × 45%
The EG Score, 5.5 of 10.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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.
EPSS PROB
0.5%
EPSS %ILE
42nd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 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 partial (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

July 14, 2026

Last Modified

October 8, 2026

Advisory Details (1)

Auto-updated Jul 15, 2026
Patch available. Sources: microsoft.
MicrosoftMentions a patch (unverified)

Security Update Guide - Microsoft Security Response Center

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55121

Vendor Advisories for CVE-2026-55121(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 51× 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 282 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 182 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  3. 2026-10-12 15:56 UTCEG score recompute
  4. 2026-10-11 19:39 UTCEG score recompute
  5. 2026-10-11 16:54 UTCEG score recompute
  6. 2026-10-11 14:17 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  10. 2026-10-08 19:15 UTCEG score recompute
  11. 2026-10-08 19:15 UTCVendor advisory
  12. 2026-10-08 19:15 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  13. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  18. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  19. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  20. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  21. 2026-10-01 12:54 UTCEG score recompute
  22. 2026-10-01 12:54 UTCVendor advisory
  23. 2026-10-01 12:54 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  24. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  25. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 41st percentile
Show 75 more
  1. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  2. 2026-09-28 08:58 UTCEG score recompute
  3. 2026-09-28 08:58 UTCVendor advisory
  4. 2026-09-28 08:58 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  5. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  6. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  7. 2026-09-25 18:40 UTCEG score recompute
  8. 2026-09-25 18:40 UTCVendor advisory
  9. 2026-09-25 18:40 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  10. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  11. 2026-09-24 09:02 UTCEG score recompute
  12. 2026-09-24 09:02 UTCVendor advisory
  13. 2026-09-24 09:02 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  14. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-09-23 03:33 UTCEG score recompute
  16. 2026-09-23 03:33 UTCVendor advisory
  17. 2026-09-23 03:33 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  18. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  19. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  20. 2026-09-17 22:52 UTCEG score recompute
  21. 2026-09-17 22:52 UTCVendor advisory
  22. 2026-09-17 22:51 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  23. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  24. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  25. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  26. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  27. 2026-09-14 05:35 UTCEG score recompute
  28. 2026-09-14 05:35 UTCVendor advisory
  29. 2026-09-14 05:35 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  30. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  31. 2026-09-13 07:41 UTCEG score recompute
  32. 2026-09-13 07:41 UTCVendor advisory
  33. 2026-09-13 07:41 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  34. 2026-09-12 01:16 UTCEG score recompute
  35. 2026-09-12 01:16 UTCVendor advisory
  36. 2026-09-12 01:16 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  37. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  38. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  39. 2026-09-09 21:07 UTCEG score recompute
  40. 2026-09-09 21:07 UTCVendor advisory
  41. 2026-09-09 21:07 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  42. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  43. 2026-09-08 21:06 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  44. 2026-09-08 17:19 UTCVendor advisory
  45. 2026-09-08 17:18 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  46. 2026-09-08 01:13 UTCEG score recompute
  47. 2026-09-08 01:13 UTCVendor advisory
  48. 2026-09-08 01:13 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  49. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  50. 2026-09-06 18:59 UTCEG score recompute
  51. 2026-09-06 18:59 UTCVendor advisory
  52. 2026-09-06 18:59 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  53. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  54. 2026-09-05 21:02 UTCEG score recompute
  55. 2026-09-05 21:02 UTCVendor advisory
  56. 2026-09-05 21:02 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  57. 2026-09-04 22:40 UTCEG score recompute
  58. 2026-09-04 22:40 UTCVendor advisory
  59. 2026-09-04 22:40 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  60. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  61. 2026-09-02 19:39 UTCEG score recompute
  62. 2026-09-02 19:39 UTCVendor advisory
  63. 2026-09-02 19:39 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  64. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  65. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  66. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  67. 2026-08-31 15:41 UTCVendor advisory
  68. 2026-08-31 15:41 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  69. 2026-08-31 02:10 UTCEG score recompute
  70. 2026-08-31 02:10 UTCVendor advisory
  71. 2026-08-31 02:10 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5
  72. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  73. 2026-08-30 04:16 UTCEG score recompute
  74. 2026-08-30 04:16 UTCVendor advisory
  75. 2026-08-30 04:16 UTCGHSA enrichmentGHSA-jvm6-p83j-gp84 · GitHub CVSS 5.5

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55121?
CVE-2026-55121 is a medium-severity vulnerability; its CVE record was published on July 14, 2026. Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
When was CVE-2026-55121 made public?
CVE-2026-55121 was made public on July 14, 2026: that is the date its CVE record's CNA, Microsoft Corporation, gives for when the vulnerability was made public. The CVE record itself was published on July 14, 2026. EchelonGraph's copy of the record carries a last-modified date of October 8, 2026; the record at its source may have been updated since.
Is CVE-2026-55121 actively exploited?
CVE-2026-55121 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (42nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55121?
CVE-2026-55121 has a CVSS base score of 5.5 (the CNA's own assessment, by microsoft; NVD's own analysis pending).
How do I remediate CVE-2026-55121?
A fix for CVE-2026-55121 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55121 are linked in the Vendor Advisories panel on this page.

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