CVE-2026-56123

CRITICALNVD 9.88.1▼
EchelonGraph scoreMEDIUM confidence

Score 8.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-06-25. NVD baseline CVSS 9.8; sources differ by 1.7.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.8Exploit: NoneExposed: 0

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
9.8
EG Score
8.1(medium)
EPSS
22.5%
KEV
Not listed

Published

June 25, 2026

Last Modified

June 26, 2026

Advisory Details (2)

Auto-updated Jun 29, 2026
Patch available.
generic

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
generic Patch Available
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 / EcosystemFixed in / PatchReleasedSource
ubuntusocat (1.8.1.1-1ubuntu0.1) @ resolute2026-07-06ubuntu

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.

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 41× in last 7d / 68× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

  1. 2026-07-07 06:20 UTCEG score recompute
  2. 2026-07-07 06:20 UTCGHSA enrichment
  3. 2026-07-06 18:47 UTCEG score recompute
  4. 2026-07-06 18:47 UTCVendor advisory
  5. 2026-07-06 18:47 UTCGHSA enrichment
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 16:27 UTCEPSS rescore
  8. 2026-07-06 07:15 UTCEG score recompute
  9. 2026-07-06 07:15 UTCGHSA enrichment
  10. 2026-07-06 02:23 UTCEPSS rescore
  11. 2026-07-06 02:23 UTCEPSS rescore
  12. 2026-07-05 19:35 UTCEG score recompute
  13. 2026-07-05 19:35 UTCGHSA enrichment
  14. 2026-07-05 08:05 UTCEG score recompute
  15. 2026-07-05 08:05 UTCGHSA enrichment
  16. 2026-07-05 02:31 UTCEPSS rescore
  17. 2026-07-05 02:30 UTCEPSS rescore
  18. 2026-07-04 20:30 UTCEG score recompute
  19. 2026-07-04 20:29 UTCGHSA enrichment
  20. 2026-07-04 08:59 UTCEG score recompute
  21. 2026-07-04 08:59 UTCGHSA enrichment
  22. 2026-07-04 06:31 UTCEPSS rescore
  23. 2026-07-04 06:31 UTCEPSS rescore
  24. 2026-07-03 21:29 UTCEG score recompute
  25. 2026-07-03 21:29 UTCGHSA enrichment
Show 43 more
  1. 2026-07-03 09:59 UTCEG score recompute
  2. 2026-07-03 09:59 UTCGHSA enrichment
  3. 2026-07-02 22:28 UTCEG score recompute
  4. 2026-07-02 22:28 UTCGHSA enrichment
  5. 2026-07-02 10:59 UTCEG score recompute
  6. 2026-07-02 10:59 UTCGHSA enrichment
  7. 2026-07-01 23:21 UTCEG score recompute
  8. 2026-07-01 23:21 UTCGHSA enrichment
  9. 2026-07-01 15:07 UTCEPSS rescore
  10. 2026-07-01 11:51 UTCEG score recompute
  11. 2026-07-01 11:50 UTCGHSA enrichment
  12. 2026-07-01 00:21 UTCEG score recompute
  13. 2026-07-01 00:20 UTCGHSA enrichment
  14. 2026-06-30 23:22 UTCEPSS rescore
  15. 2026-06-30 12:50 UTCEG score recompute
  16. 2026-06-30 12:49 UTCGHSA enrichment
  17. 2026-06-30 01:18 UTCEG score recompute
  18. 2026-06-30 01:18 UTCGHSA enrichment
  19. 2026-06-29 14:06 UTCEPSS rescore
  20. 2026-06-29 14:06 UTCEPSS rescore
  21. 2026-06-29 13:48 UTCEG score recompute
  22. 2026-06-29 13:48 UTCGHSA enrichment
  23. 2026-06-29 02:18 UTCEG score recompute
  24. 2026-06-29 02:18 UTCGHSA enrichment
  25. 2026-06-28 14:48 UTCEG score recompute
  26. 2026-06-28 14:48 UTCGHSA enrichment
  27. 2026-06-28 14:07 UTCEPSS rescore
  28. 2026-06-28 04:56 UTCEPSS rescore
  29. 2026-06-28 04:56 UTCEPSS rescore
  30. 2026-06-28 03:18 UTCEG score recompute
  31. 2026-06-28 03:18 UTCGHSA enrichment
  32. 2026-06-27 15:48 UTCEG score recompute
  33. 2026-06-27 15:48 UTCGHSA enrichment
  34. 2026-06-27 04:18 UTCEG score recompute
  35. 2026-06-27 04:18 UTCGHSA enrichment
  36. 2026-06-27 03:08 UTCEPSS rescore
  37. 2026-06-26 17:41 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  38. 2026-06-26 16:48 UTCEG score recompute
  39. 2026-06-26 16:48 UTCGHSA enrichment
  40. 2026-06-26 05:19 UTCEG score recompute
  41. 2026-06-26 05:19 UTCGHSA enrichment
  42. 2026-06-25 17:49 UTCEG score recompute
  43. 2026-06-25 17:48 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-56123?
CVE-2026-56123 is a critical vulnerability 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 disclosed?
CVE-2026-56123 was first published in the National Vulnerability Database on June 25, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56123 actively exploited?
CVE-2026-56123 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 22.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-56123?
CVE-2026-56123 has a CVSS v3 base score of 9.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.1.
How do I remediate CVE-2026-56123?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56123, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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