CVE-2026-23556

CRITICALPre-NVD 9.49.4
EchelonGraph scoreMEDIUM confidence

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

This critical-severity CVE scores 9.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (3rd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source

Also known asEUVD-2026-42600 (ENISA EUVD) · GHSA-qcp2-2xf6-hw26 (GitHub Security Advisories)Source: ENISA EUVD

9.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 9.4Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

When oxenstored is tearing a domain down, the node data is cleaned up but the usage counts are leaked.

When the domain ID is eventually reused, the new domain can create fewer nodes before beeing deemed to be over quota.

CVSS
9.4
EG Score
9.4CRITICALmedium confidence
EG Risk
42
EG Risk 42/100

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)
Severity94% × 45%
Impact severity (EG Severity): CVSS 9.4 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 low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (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.
EPSS PROB
0.1%
EPSS %ILE
3rd
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 (9.4): severity, escalated by confirmed exploitation. This CVE's 9.4 is its impact severity (EG Severity), not escalated.

EG Severity
9.4 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source
EG Likelihood
0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-13). 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 low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation none (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.

The score's inputs: 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

July 9, 2026

Last Modified

October 25, 2026

Advisory Details (3)

Auto-updated Oct 2, 2026
Patch available.
Web page

XSA-483 - Xen Security Advisories

http://xenbits.xen.org/xsa/advisory-483.html
Web page

oss-security - Xen Security Advisory 483 v2 (CVE-2026-23556) - oxenstored keeps quota related use counts across domain destruction

http://www.openwall.com/lists/oss-security/2026/04/28/10
Web page

XSA-483 - Xen Security Advisories

https://xenbits.xen.org/xsa/advisory-483.html

Vendor Advisories for CVE-2026-23556(1)

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

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.14.2+25-gb6a8c4f72d-2 ... 4.20.3+127-gc42374a105-1 (46 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.17.1+2-gb773c48e36-1 ... 4.17.5+72-g01140da4e8-1 (14 versions)
  • every version up to 4.17.7-0+deb12u1: fixed in 4.17.7-0+deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.20.0+68-g35cb38b222-1 ... 4.20.2+7-g1badcf5035-2 (6 versions)
  • every version up to 4.20.3+127-gc42374a105-0+deb13u1: fixed in 4.20.3+127-gc42374a105-0+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.20.0+68-g35cb38b222-1, 4.20.2+37-g61ff35323e-1, 4.20.2+7-g1badcf5035-1, 4.20.2+7-g1badcf5035-2
  • every version up to 4.20.3+127-gc42374a105-1: fixed in 4.20.3+127-gc42374a105-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 60× 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 its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS → 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 477 rows 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 377 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 19:21 UTCEchelonGraph re-scored
  2. 2026-11-13 19:21 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  3. 2026-11-13 16:51 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  4. 2026-11-12 19:11 UTCEchelonGraph re-scored
  5. 2026-11-12 19:11 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  6. 2026-11-11 20:11 UTCEchelonGraph re-scored
  7. 2026-11-11 20:11 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  8. 2026-11-11 16:39 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  9. 2026-11-10 21:14 UTCEchelonGraph re-scored
  10. 2026-11-10 21:14 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  11. 2026-11-10 16:43 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  12. 2026-11-09 22:15 UTCEchelonGraph re-scored
  13. 2026-11-09 22:15 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  14. 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  15. 2026-11-08 23:16 UTCEchelonGraph re-scored
  16. 2026-11-08 23:16 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  17. 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  18. 2026-11-08 00:20 UTCEchelonGraph re-scored
  19. 2026-11-08 00:20 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  20. 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  21. 2026-11-07 01:24 UTCEchelonGraph re-scored
  22. 2026-11-07 01:24 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  23. 2026-11-06 16:37 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  24. 2026-11-06 02:28 UTCEchelonGraph re-scored
  25. 2026-11-06 02:28 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
Show 75 more
  1. 2026-11-05 16:37 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  2. 2026-11-05 03:32 UTCEchelonGraph re-scored
  3. 2026-11-05 03:32 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  4. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  5. 2026-11-04 04:36 UTCEchelonGraph re-scored
  6. 2026-11-04 04:36 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  7. 2026-11-03 16:47 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  8. 2026-11-03 05:40 UTCEchelonGraph re-scored
  9. 2026-11-03 05:40 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  10. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  11. 2026-11-02 06:43 UTCEchelonGraph re-scored
  12. 2026-11-02 06:43 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  13. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  14. 2026-11-01 07:47 UTCEchelonGraph re-scored
  15. 2026-11-01 07:47 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  16. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  17. 2026-10-31 08:51 UTCEchelonGraph re-scored
  18. 2026-10-31 08:51 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  19. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  20. 2026-10-30 09:55 UTCEchelonGraph re-scored
  21. 2026-10-30 09:55 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  22. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  23. 2026-10-29 11:00 UTCEchelonGraph re-scored
  24. 2026-10-29 11:00 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  25. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  26. 2026-10-28 11:51 UTCEchelonGraph re-scored
  27. 2026-10-28 11:51 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  28. 2026-10-27 12:50 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  29. 2026-10-26 16:37 UTCEchelonGraph re-scored
  30. 2026-10-26 16:37 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  31. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  32. 2026-10-25 17:27 UTCEchelonGraph re-scored
  33. 2026-10-25 17:27 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  34. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  35. 2026-10-25 14:41 UTCEchelonGraph re-scored
  36. 2026-10-25 02:43 UTCEchelonGraph re-scored
  37. 2026-10-25 02:43 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  38. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  39. 2026-10-24 03:47 UTCEchelonGraph re-scored
  40. 2026-10-24 03:47 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  41. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  42. 2026-10-23 04:49 UTCEchelonGraph re-scored
  43. 2026-10-23 04:49 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  44. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  45. 2026-10-22 05:51 UTCEchelonGraph re-scored
  46. 2026-10-22 05:51 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  47. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  48. 2026-10-21 06:52 UTCEchelonGraph re-scored
  49. 2026-10-21 06:52 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  50. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  51. 2026-10-20 07:53 UTCEchelonGraph re-scored
  52. 2026-10-20 07:53 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  53. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  54. 2026-10-19 08:55 UTCEchelonGraph re-scored
  55. 2026-10-19 08:55 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  56. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  57. 2026-10-18 09:56 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  58. 2026-10-18 03:54 UTCEchelonGraph re-scored
  59. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  60. 2026-10-17 06:51 UTCEchelonGraph re-scored
  61. 2026-10-17 06:50 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  62. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  63. 2026-10-16 07:52 UTCEchelonGraph re-scored
  64. 2026-10-16 07:52 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  65. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  66. 2026-10-15 06:53 UTCEchelonGraph re-scored
  67. 2026-10-15 06:53 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  68. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  69. 2026-10-14 02:39 UTCEchelonGraph re-scored
  70. 2026-10-14 02:38 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  71. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  72. 2026-10-12 22:51 UTCEchelonGraph re-scored
  73. 2026-10-12 22:50 UTCGHSA enrichmentGHSA-qcp2-2xf6-hw26 · GitHub severity CRITICAL
  74. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  75. 2026-10-12 16:21 UTCEchelonGraph re-scored

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-23556?
CVE-2026-23556 is a critical-severity vulnerability; its CVE record was published on July 9, 2026. When oxenstored is tearing a domain down, the node data is cleaned up but the usage counts are leaked. When the domain ID is eventually reused, the new domain can create fewer nodes before beeing deemed to be over quota.
When was the CVE record for CVE-2026-23556 published?
The CVE record for CVE-2026-23556 was published on July 9, 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 October 25, 2026; the record at its source may have been updated since.
Is CVE-2026-23556 actively exploited?
CVE-2026-23556 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (3rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-23556?
CVE-2026-23556 has a CVSS base score of 9.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-23556?
A fix for CVE-2026-23556 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-23556 are linked in the Vendor Advisories panel on this page.

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