CVE-2026-16855

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 2026-08-19. A secondary CVSS source baseline 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
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: 0.1%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to cause a denial of service due to a heap buffer overflow.

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 impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity55% × 45%
Impact severity (EG Severity): CVSS 5.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.1% × 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 referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines; until then, restrict network exposure of the affected system or apply the vendor's mitigation.
EPSS PROB
0.1%
EPSS %ILE
2nd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.

EG Severity
5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

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

A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines; until then, restrict network exposure of the affected system or apply the vendor's mitigation.

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

August 19, 2026

Last Modified

August 24, 2026

Advisory Details (1)

Auto-updated Aug 19, 2026
Fix referenced — no release confirmed yet.
Web page

Security Bulletin: Vulnerabilities in IBM AIX and PowerVM VIOS

https://www.ibm.com/support/pages/node/7283858

Vendor Advisories for CVE-2026-16855(1)

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 8× in last 7d / 54× 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 139 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 39 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  2. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  3. 2026-10-18 04:00 UTCEG score recompute
  4. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  5. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  6. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  7. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  8. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  9. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  10. 2026-10-12 16:29 UTCEG score recompute
  11. 2026-10-11 20:08 UTCEG score recompute
  12. 2026-10-11 17:21 UTCEG score recompute
  13. 2026-10-11 14:54 UTCEG score recompute
  14. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  15. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  16. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  17. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  18. 2026-10-08 08:23 UTCEG score recompute
  19. 2026-10-08 08:23 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  20. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  21. 2026-10-07 07:59 UTCEG score recompute
  22. 2026-10-07 07:59 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  23. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  24. 2026-10-06 07:55 UTCEG score recompute
  25. 2026-10-06 07:55 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
Show 75 more
  1. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  2. 2026-10-04 21:24 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  3. 2026-10-03 16:54 UTCEG score recompute
  4. 2026-10-03 16:54 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  5. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  6. 2026-10-02 09:13 UTCEG score recompute
  7. 2026-10-02 09:13 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  8. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  9. 2026-10-01 08:43 UTCEG score recompute
  10. 2026-10-01 08:43 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  11. 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  12. 2026-09-30 08:39 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  13. 2026-09-29 06:11 UTCEG score recompute
  14. 2026-09-29 06:11 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  15. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  16. 2026-09-28 06:06 UTCEG score recompute
  17. 2026-09-28 06:06 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  18. 2026-09-27 13:47 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  19. 2026-09-27 06:02 UTCEG score recompute
  20. 2026-09-27 06:02 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  21. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  22. 2026-09-25 04:05 UTCEG score recompute
  23. 2026-09-25 04:05 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  24. 2026-09-24 04:01 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  25. 2026-09-23 03:57 UTCEG score recompute
  26. 2026-09-23 03:57 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  27. 2026-09-22 03:53 UTCEG score recompute
  28. 2026-09-22 03:53 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  29. 2026-09-21 03:48 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  30. 2026-09-20 03:44 UTCEG score recompute
  31. 2026-09-20 03:44 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  32. 2026-09-19 03:40 UTCEG score recompute
  33. 2026-09-19 03:40 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  34. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  35. 2026-09-18 03:36 UTCEG score recompute
  36. 2026-09-18 03:36 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  37. 2026-09-17 03:32 UTCEG score recompute
  38. 2026-09-17 03:32 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  39. 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  40. 2026-09-16 05:14 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  41. 2026-09-16 03:02 UTCEG score recompute
  42. 2026-09-16 03:02 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  43. 2026-09-15 02:58 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  44. 2026-09-14 02:54 UTCEG score recompute
  45. 2026-09-14 02:54 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  46. 2026-09-13 16:46 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  47. 2026-09-13 02:49 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  48. 2026-09-12 02:44 UTCEG score recompute
  49. 2026-09-12 02:44 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  50. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  51. 2026-09-11 09:36 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  52. 2026-09-11 02:40 UTCEG score recompute
  53. 2026-09-11 02:39 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  54. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  55. 2026-09-10 02:35 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  56. 2026-09-09 02:31 UTCEG score recompute
  57. 2026-09-09 02:31 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  58. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  59. 2026-09-07 21:45 UTCEG score recompute
  60. 2026-09-07 21:45 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  61. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  62. 2026-09-06 21:41 UTCEG score recompute
  63. 2026-09-06 21:41 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  64. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  65. 2026-09-05 21:37 UTCEG score recompute
  66. 2026-09-05 21:37 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  67. 2026-09-04 21:32 UTCEG score recompute
  68. 2026-09-04 21:32 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  69. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  70. 2026-09-03 21:23 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  71. 2026-09-02 21:16 UTCEG score recompute
  72. 2026-09-02 21:16 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5
  73. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.1% · below the 1st percentile
  74. 2026-09-01 19:56 UTCEG score recompute
  75. 2026-09-01 19:56 UTCGHSA enrichmentGHSA-r7x9-3h4v-9mc9 · GitHub CVSS 5.5

Frequently asked(5)

What is CVE-2026-16855?
CVE-2026-16855 is a medium-severity vulnerability; its CVE record was published on August 19, 2026. IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to cause a denial of service due to a heap buffer overflow.
When was the CVE record for CVE-2026-16855 published?
The CVE record for CVE-2026-16855 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 August 24, 2026; the record at its source may have been updated since.
Is CVE-2026-16855 actively exploited?
CVE-2026-16855 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (2nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-16855?
CVE-2026-16855 has a CVSS base score of 5.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-16855?
A fix for CVE-2026-16855 is referenced (a reference tagged "Patch", often a source commit), but EchelonGraph has no release containing it on record. Check that reference and the vendor's advisory for a release that contains the fix and update to it; until then, restrict network exposure of the affected system or apply the vendor's mitigation. The vendor advisories EchelonGraph has for CVE-2026-16855 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-16855

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