CVE-2026-56123

HIGHPre-NVD 8.18.1
EchelonGraph scoreMEDIUM confidence

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

Score 8.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-06-25. The CNA's CVSS baseline 8.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: the CNA's CVSS, EPSS, GitHub Security Advisory
Trending — 3 sources updated this week

Also known asEUVD-2026-39455 (ENISA EUVD) · GHSA-6r8c-w5mj-43hv (GitHub Security Advisories)Source: ENISA EUVD

8.1EG
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: 0.3%CVSS: 8.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOCKS5 proxy server to overwrite adjacent heap memory by exploiting a sign-extension flaw in the DOMAINNAME reply parser. During connection setup, the domain name length byte is read through a signed char field causing a negative bytes_to_read value that is implicitly converted to size_t, resulting in an unbounded heap write into the 262-byte reply buffer with attacker-controlled size and content.

CVSS v3
8.1
EG Score
8.1HIGHmedium confidence
EG Risk
37
EG Risk 37/100

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)
Severity81% × 45%
Impact severity (EG Severity): CVSS 8.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 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
0.3%
EPSS %ILE
24th
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 (8.1): severity, escalated by confirmed exploitation. This CVE's 8.1 is its impact severity (EG Severity), not escalated.

EG Severity
8.1 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-30). 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

June 25, 2026

Last Modified

July 14, 2026

Advisory Details (2)

Auto-updated Jul 12, 2026
Patch available.
Web page

socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser | Advisories | VulnCheck

https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser
Web pageMentions a patch (unverified)
http://www.dest-unreach.org/socat/CHANGES

Vendor Advisories for CVE-2026-56123(2)

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

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntusocat (1.8.1.1-1ubuntu0.1) @ resolute2026-10-24ubuntu

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

(6 across 6 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
socat—
  • 1.8.0.0 up to 1.8.1.2-r0: fixed in 1.8.1.2-r0
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
socat—
  • 1.8.0.0 up to 1.8.1.2-r0: fixed in 1.8.1.2-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
socat—
  • 1.8.0.0 up to 1.8.1.2-r0: fixed in 1.8.1.2-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
socat—
  • 1.8.0.0 up to 1.8.1.2-r0: fixed in 1.8.1.2-r0
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
socat1.8.0.3-1
  • every version up to 1.8.0.3-1+deb13u1: fixed in 1.8.0.3-1+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
socat1.8.0.3-1, 1.8.1.0-1, 1.8.1.0-2, 1.8.1.1-1, 1.8.1.1-2
  • every version up to 1.8.1.3-1: fixed in 1.8.1.3-1
—

Weakness Classification(1)

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 9× in last 7d / 42× 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 356 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 256 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  3. 2026-10-31 01:50 UTCEG score recompute
  4. 2026-10-31 01:50 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  11. 2026-10-25 14:18 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  13. 2026-10-24 02:29 UTCEG score recompute
  14. 2026-10-24 02:29 UTCVendor advisory
  15. 2026-10-24 02:29 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  16. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  17. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  18. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  19. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  20. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  21. 2026-10-18 03:29 UTCEG score recompute
  22. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  23. 2026-10-17 03:07 UTCEG score recompute
  24. 2026-10-17 03:06 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  25. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
Show 75 more
  1. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  2. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  3. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  5. 2026-10-12 15:55 UTCEG score recompute
  6. 2026-10-11 19:38 UTCEG score recompute
  7. 2026-10-11 16:53 UTCEG score recompute
  8. 2026-10-11 14:16 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  12. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  13. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  14. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  15. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  16. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  17. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  18. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  19. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  20. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  21. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  22. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  24. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  25. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  26. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  27. 2026-09-23 08:44 UTCEG score recompute
  28. 2026-09-23 08:44 UTCVendor advisory
  29. 2026-09-23 08:44 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  30. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  31. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  32. 2026-09-18 07:22 UTCEG score recompute
  33. 2026-09-18 07:22 UTCVendor advisory
  34. 2026-09-18 07:22 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  35. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  36. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  37. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  38. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  39. 2026-09-14 01:18 UTCEG score recompute
  40. 2026-09-14 01:18 UTCVendor advisory
  41. 2026-09-14 01:18 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  42. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  43. 2026-09-13 09:38 UTCVendor advisory
  44. 2026-09-13 09:38 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  45. 2026-09-12 15:46 UTCEG score recompute
  46. 2026-09-12 15:46 UTCVendor advisory
  47. 2026-09-12 15:46 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  48. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  49. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  50. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  51. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  52. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  53. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  54. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  55. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  56. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  57. 2026-08-30 19:32 UTCEG score recompute
  58. 2026-08-30 19:32 UTCVendor advisory
  59. 2026-08-30 19:32 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  60. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  61. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  62. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  63. 2026-08-27 23:20 UTCEG score recompute
  64. 2026-08-27 23:20 UTCVendor advisory
  65. 2026-08-27 23:20 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  66. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  67. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  68. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  69. 2026-08-25 00:46 UTCEG score recompute
  70. 2026-08-25 00:46 UTCVendor advisory
  71. 2026-08-25 00:46 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  72. 2026-08-24 13:09 UTCEG score recompute
  73. 2026-08-24 13:09 UTCVendor advisory
  74. 2026-08-24 13:09 UTCGHSA enrichmentGHSA-6r8c-w5mj-43hv · GitHub severity CRITICAL · GitHub CVSS 8.1
  75. 2026-08-23 21:25 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-56123?
CVE-2026-56123 is a high-severity vulnerability; its CVE record was published on June 25, 2026. socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOCKS5 proxy server to overwrite adjacent heap memory by exploiting a sign-extension flaw in the DOMAINNAME reply parser. During connection setup, the domain name length byte is read…
When was CVE-2026-56123 made public?
CVE-2026-56123 was made public on June 25, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on June 25, 2026. EchelonGraph's copy of the record carries a last-modified date of July 14, 2026; the record at its source may have been updated since.
Is CVE-2026-56123 actively exploited?
CVE-2026-56123 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-56123?
CVE-2026-56123 has a CVSS base score of 8.1 (the CNA's own assessment, by vulncheck; NVD's own analysis pending).
How do I remediate CVE-2026-56123?
A fix for CVE-2026-56123 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-56123 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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