CVE-2026-42790

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 74% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 4 sources updated this week
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.1Exploit: None knownExposed: 0

A fix is available — apply it.

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification.

Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g. permitted;DNS:allowed.example.com) to issue a leaf certificate that an OTP TLS client accepts as a valid identity for an out-of-scope hostname (e.g. victim.example.com):

First, pubkey_cert:validate_names/6 in lib/public_key/src/pubkey_cert.erl only checks SAN DNS entries against nameConstraints. Per RFC 5280, a permitted DNS subtree only restricts certificates that contain a DNS-typed name. A leaf with no subjectAltName therefore trivially satisfies any permitted;DNS:... constraint regardless of its subject commonName.

Second, public_key:pkix_verify_hostname/3 in lib/public_key/src/public_key.erl falls back to the subject commonName when no subjectAltName is present, extracting id-at-commonName attributes as presented IDs and matching them against the reference hostname. The strict pkix_verify_hostname_match_fun(https) matcher does not suppress this fallback.

The result is that path validation accepts a CN-only leaf under a DNS-constrained intermediate (no SAN means the nameConstraints are not triggered), and hostname verification then accepts it via the CN fallback. The bypass is reachable from stock ssl:connect with verify_peer, a trusted CA, SNI, and the canonical strict https hostname matcher.

This issue affects OTP from OTP 19.3 before OTP 29.0.1, OTP 28.5.0.1, OTP 27.3.4.12 and OTP 26.2.5.21, corresponding to public_key from 1.4 before 1.21.1, 1.20.3.1, 1.17.1.3 and 1.15.1.7.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
37(Track)
EG Risk 37/100SSVC: Track

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
Severity81% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
26%
KEV
Not listed

Published

May 27, 2026

Last Modified

July 24, 2026

Advisory Details (7)

Auto-updated Jun 3, 2026
Patch available. Sources: github_commit, github.
generic

Versions — Erlang System Documentation v29.0.1

https://www.erlang.org/doc/system/versions.html#order-of-versions
generic

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-42790
github Patch Available

Name Constraints and Subject CommonName Fallback in TLS hostname Verification · Advisory · erlang/otp · GitHub

https://github.com/erlang/otp/security/advisories/GHSA-22cw-4ph4-6447
github_commit

commit fb67c6d1836f (erlang/otp)

Fix landed in erlang/otp commit fb67c6d1836f — awaiting tagged release

https://github.com/erlang/otp/commit/fb67c6d1836f51105a96d8b769e71e4215a79457
github_commit

commit 21abed64eb20 (erlang/otp)

Fix landed in erlang/otp commit 21abed64eb20 — awaiting tagged release

https://github.com/erlang/otp/commit/21abed64eb2026b5f82f432709e4e932f9be389a
github_commit

commit 0769050c69d7 (erlang/otp)

Fix landed in erlang/otp commit 0769050c69d7 — awaiting tagged release

https://github.com/erlang/otp/commit/0769050c69d73762672b0db1347b6993a5b31759
generic

nameConstraints DNS bypass via subject CommonName fallback in public_key hostname verification | Erlang Ecosystem Foundation CNA

https://cna.erlef.org/cves/CVE-2026-42790.html

Vendor Advisories for CVE-2026-42790(1)

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
redhaterlang-0:26.2.5.21-2.el9ost2026-07-15redhat

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(2)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 14× in last 7d / 53× 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.

Showing the most recent 100 of 120 total refreshes for this CVE.

  1. 2026-07-27 14:13 UTCEPSS rescore
  2. 2026-07-27 10:09 UTCEG score recompute
  3. 2026-07-27 10:09 UTCVendor advisory
  4. 2026-07-26 14:54 UTCEPSS rescore
  5. 2026-07-26 14:54 UTCEPSS rescore
  6. 2026-07-26 07:39 UTCEG score recompute▲ 0.70
  7. 2026-07-26 07:39 UTCVendor advisory
  8. 2026-07-25 14:18 UTCEPSS rescore
  9. 2026-07-24 16:11 UTCNVD updateCVSS v3 → 8.1
  10. 2026-07-24 14:17 UTCEPSS rescore
  11. 2026-07-23 14:18 UTCEPSS rescore
  12. 2026-07-23 03:11 UTCEG score recompute
  13. 2026-07-22 14:08 UTCEPSS rescore
  14. 2026-07-21 15:24 UTCEPSS rescore
  15. 2026-07-20 17:08 UTCEPSS rescore
  16. 2026-07-19 14:31 UTCEPSS rescore
  17. 2026-07-19 02:29 UTCEPSS rescore
  18. 2026-07-18 10:04 UTCEPSS rescore
  19. 2026-07-16 17:03 UTCEPSS rescore
  20. 2026-07-16 04:28 UTCMITRE cvelistV5CVSS v3 → 7.4
  21. 2026-07-15 16:57 UTCEPSS rescore
  22. 2026-07-15 14:22 UTCNVD updateCVSS v3 → 8.1
  23. 2026-07-15 04:19 UTCMITRE cvelistV5CVSS v3 → 7.4
  24. 2026-07-15 02:26 UTCNVD updateCVSS v3 → 8.1
  25. 2026-07-15 02:00 UTCEPSS rescore
Show 75 more
  1. 2026-07-13 22:30 UTCEPSS rescore
  2. 2026-07-13 06:13 UTCEPSS rescore
  3. 2026-07-12 05:46 UTCEPSS rescore
  4. 2026-07-11 23:17 UTCVendor advisory
  5. 2026-07-11 08:27 UTCEPSS rescore
  6. 2026-07-09 19:10 UTCEPSS rescore
  7. 2026-07-08 23:45 UTCEG score recompute▼ 0.70
  8. 2026-07-08 23:45 UTCVendor advisory
  9. 2026-07-08 15:16 UTCEPSS rescore
  10. 2026-07-07 13:46 UTCEPSS rescore
  11. 2026-07-06 16:27 UTCEPSS rescore
  12. 2026-07-06 16:27 UTCEPSS rescore
  13. 2026-07-06 02:23 UTCEPSS rescore
  14. 2026-07-06 02:23 UTCEPSS rescore
  15. 2026-07-05 02:30 UTCEPSS rescore
  16. 2026-07-04 06:31 UTCEPSS rescore
  17. 2026-07-03 17:46 UTCMITRE cvelistV5CVSS v3 → 7.4
  18. 2026-07-01 15:06 UTCEPSS rescore
  19. 2026-07-01 09:32 UTCVendor advisory
  20. 2026-06-30 23:22 UTCEPSS rescore
  21. 2026-06-30 03:13 UTCVendor advisory
  22. 2026-06-29 14:07 UTCVendor advisory
  23. 2026-06-29 14:06 UTCEPSS rescore
  24. 2026-06-28 19:26 UTCVendor advisory
  25. 2026-06-28 14:07 UTCEPSS rescore
  26. 2026-06-28 06:40 UTCVendor advisory
  27. 2026-06-28 04:56 UTCEPSS rescore
  28. 2026-06-27 18:25 UTCVendor advisory
  29. 2026-06-27 05:44 UTCVendor advisory
  30. 2026-06-27 03:08 UTCEPSS rescore
  31. 2026-06-26 17:03 UTCVendor advisory
  32. 2026-06-26 02:23 UTCVendor advisory
  33. 2026-06-25 13:49 UTCEPSS rescore
  34. 2026-06-25 13:49 UTCEPSS rescore
  35. 2026-06-25 12:13 UTCVendor advisory
  36. 2026-06-25 00:27 UTCVendor advisory
  37. 2026-06-24 14:05 UTCEPSS rescore
  38. 2026-06-23 21:33 UTCEPSS rescore
  39. 2026-06-22 14:25 UTCEPSS rescore
  40. 2026-06-22 14:25 UTCEPSS rescore
  41. 2026-06-21 14:56 UTCEPSS rescore
  42. 2026-06-21 14:56 UTCEPSS rescore
  43. 2026-06-21 01:59 UTCEPSS rescore
  44. 2026-06-19 19:25 UTCEPSS rescore
  45. 2026-06-18 17:52 UTCEPSS rescore
  46. 2026-06-18 17:52 UTCEPSS rescore
  47. 2026-06-17 17:53 UTCEPSS rescore
  48. 2026-06-16 21:46 UTCVendor advisory
  49. 2026-06-16 17:52 UTCEPSS rescore
  50. 2026-06-16 10:04 UTCVendor advisory
  51. 2026-06-15 22:16 UTCVendor advisory
  52. 2026-06-15 17:49 UTCEPSS rescore
  53. 2026-06-15 07:48 UTCVendor advisory
  54. 2026-06-14 20:00 UTCVendor advisory
  55. 2026-06-14 08:16 UTCVendor advisory
  56. 2026-06-13 23:00 UTCEPSS rescore
  57. 2026-06-13 06:17 UTCVendor advisory
  58. 2026-06-12 23:12 UTCEPSS rescore
  59. 2026-06-12 23:12 UTCEPSS rescore
  60. 2026-06-12 18:30 UTCVendor advisory
  61. 2026-06-12 06:47 UTCVendor advisory
  62. 2026-06-11 19:05 UTCVendor advisory
  63. 2026-06-11 14:00 UTCEPSS rescore
  64. 2026-06-11 07:22 UTCVendor advisory
  65. 2026-06-10 22:18 UTCEPSS rescore
  66. 2026-06-10 19:40 UTCVendor advisory
  67. 2026-06-10 13:22 UTCEPSS rescore
  68. 2026-06-10 13:22 UTCEPSS rescore
  69. 2026-06-10 07:58 UTCVendor advisory
  70. 2026-06-09 20:16 UTCVendor advisory
  71. 2026-06-09 08:31 UTCVendor advisory
  72. 2026-06-08 14:17 UTCEPSS rescore
  73. 2026-06-08 14:17 UTCEPSS rescore
  74. 2026-06-07 15:25 UTCEPSS rescore
  75. 2026-06-07 15:25 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-42790?
CVE-2026-42790 is a high vulnerability published on May 27, 2026. Improper Certificate Validation vulnerability in Erlang OTP publickey (pubkeycert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g.…
When was CVE-2026-42790 disclosed?
CVE-2026-42790 was first published in the National Vulnerability Database on May 27, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42790 actively exploited?
CVE-2026-42790 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.7% of all scored CVEs.
What is the CVSS score of CVE-2026-42790?
CVE-2026-42790 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-42790?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42790, 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.

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