CVE-2026-42789

MEDIUMNVD 4.84.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.8 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 75% 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
4.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.8Exploit: None knownExposed: 0

A fix is available — apply it.

Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP public_key (pubkey_cert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery.

In lib/public_key/src/pubkey_cert.erl, pubkey_cert:validate_extensions/7 contains two flaws that together allow a certificate with basicConstraints cA:false and no keyUsage extension to be used as an intermediate issuer in a chain passed to public_key:pkix_path_validation/3: the cA:false clause recurses into the remaining extensions without rejecting the certificate when it is in issuer position, and the keyUsage check only fires when the extension is present, so a certificate lacking keyUsage entirely bypasses the keyCertSign enforcement.

Any party holding an end-entity certificate with basicConstraints cA:false and no keyUsage extension, issued by any CA in the victim's trust store, can use that certificate's private key to sign forged leaf certificates for arbitrary identities. public_key:pkix_path_validation/3 accepts the resulting chain, and by extension every TLS or mTLS endpoint built on the OTP ssl application that relies on the default verifier is affected, including server identity verification on the client side and client certificate verification on mTLS servers.

This issue affects OTP from OTP 17.0 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 0.22 before 1.21.1, 1.20.3.1, 1.17.1.3 and 1.15.1.7.

CVSS v3
4.8
EG Score
4.8(medium)
EG Risk
22(Track)
EG Risk 22/100SSVC: 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
Severity48% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
25%
KEV
Not listed

Published

May 27, 2026

Last Modified

July 24, 2026

Advisory Details (6)

Auto-updated Jun 15, 2026
Patch available. Sources: github_commit, github.
generic

Versions — Erlang System Documentation v29.0.2

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

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-42789
github Patch Available

public_key Accepts non-CA Certificate as Intermediate Issuer, Enabling Chain Forgery · Advisory · erlang/otp · GitHub

https://github.com/erlang/otp/security/advisories/GHSA-c99q-jmpx-v8qq
github_commit

commit 59c8d824386b (erlang/otp)

Fix landed in erlang/otp commit 59c8d824386b — awaiting tagged release

https://github.com/erlang/otp/commit/59c8d824386b2eb1614ff9340624843ef6aca0fd
github_commit

commit 471cd2f66430 (erlang/otp)

Fix landed in erlang/otp commit 471cd2f66430 — awaiting tagged release

https://github.com/erlang/otp/commit/471cd2f664300a95353c467873800bbe706005db
generic

Non-CA certificate accepted as intermediate issuer in public_key path validation | Erlang Ecosystem Foundation CNA

https://cna.erlef.org/cves/CVE-2026-42789.html

Vendor Advisories for CVE-2026-42789(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 12× in last 7d / 47× 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 104 total refreshes for this CVE.

  1. 2026-07-26 14:54 UTCEPSS rescore
  2. 2026-07-26 14:54 UTCEPSS rescore
  3. 2026-07-26 07:39 UTCEG score recompute▼ 3.20
  4. 2026-07-26 07:39 UTCVendor advisory
  5. 2026-07-25 14:18 UTCEPSS rescore
  6. 2026-07-24 16:11 UTCNVD updateCVSS v3 → 4.8 · severity → MEDIUM
  7. 2026-07-24 14:17 UTCEPSS rescore
  8. 2026-07-23 14:18 UTCEPSS rescore
  9. 2026-07-23 03:11 UTCEG score recompute
  10. 2026-07-22 14:08 UTCEPSS rescore
  11. 2026-07-21 15:24 UTCEPSS rescore
  12. 2026-07-20 17:08 UTCEPSS rescore
  13. 2026-07-19 14:31 UTCEPSS rescore
  14. 2026-07-19 02:29 UTCEPSS rescore
  15. 2026-07-18 10:04 UTCEPSS rescore
  16. 2026-07-16 17:03 UTCEPSS rescore
  17. 2026-07-16 04:28 UTCMITRE cvelistV5CVSS v3 → 8 · severity → HIGH
  18. 2026-07-15 16:57 UTCEPSS rescore
  19. 2026-07-15 14:22 UTCNVD updateCVSS v3 → 4.8 · severity → MEDIUM
  20. 2026-07-15 04:19 UTCMITRE cvelistV5CVSS v3 → 8 · severity → HIGH
  21. 2026-07-15 02:25 UTCNVD updateCVSS v3 → 4.8 · severity → MEDIUM
  22. 2026-07-15 02:00 UTCEPSS rescore
  23. 2026-07-13 22:30 UTCEPSS rescore
  24. 2026-07-13 06:13 UTCEPSS rescore
  25. 2026-07-12 05:46 UTCEPSS rescore
Show 75 more
  1. 2026-07-12 01:11 UTCVendor advisory
  2. 2026-07-11 08:27 UTCEPSS rescore
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-09 00:18 UTCEG score recompute▲ 3.20
  5. 2026-07-09 00:18 UTCVendor advisory
  6. 2026-07-08 15:16 UTCEPSS rescore
  7. 2026-07-07 13:46 UTCEPSS rescore
  8. 2026-07-06 16:27 UTCEPSS rescore
  9. 2026-07-06 16:27 UTCEPSS rescore
  10. 2026-07-06 02:23 UTCEPSS rescore
  11. 2026-07-06 02:23 UTCEPSS rescore
  12. 2026-07-05 02:30 UTCEPSS rescore
  13. 2026-07-04 06:31 UTCEPSS rescore
  14. 2026-07-03 17:46 UTCMITRE cvelistV5CVSS v3 → 8 · severity → HIGH
  15. 2026-07-01 15:06 UTCEPSS rescore
  16. 2026-07-01 11:12 UTCVendor advisory
  17. 2026-06-30 23:22 UTCEPSS rescore
  18. 2026-06-29 14:27 UTCVendor advisory
  19. 2026-06-29 14:06 UTCEPSS rescore
  20. 2026-06-28 14:07 UTCEPSS rescore
  21. 2026-06-28 07:27 UTCVendor advisory
  22. 2026-06-28 04:56 UTCEPSS rescore
  23. 2026-06-27 06:07 UTCVendor advisory
  24. 2026-06-27 03:08 UTCEPSS rescore
  25. 2026-06-26 02:54 UTCVendor advisory
  26. 2026-06-25 13:49 UTCEPSS rescore
  27. 2026-06-25 13:49 UTCEPSS rescore
  28. 2026-06-25 01:33 UTCVendor advisory
  29. 2026-06-24 14:05 UTCEPSS rescore
  30. 2026-06-23 21:33 UTCEPSS rescore
  31. 2026-06-22 14:25 UTCEPSS rescore
  32. 2026-06-22 14:25 UTCEPSS rescore
  33. 2026-06-21 14:56 UTCEPSS rescore
  34. 2026-06-21 14:56 UTCEPSS rescore
  35. 2026-06-21 01:59 UTCEPSS rescore
  36. 2026-06-19 19:25 UTCEPSS rescore
  37. 2026-06-18 17:52 UTCEPSS rescore
  38. 2026-06-18 17:52 UTCEPSS rescore
  39. 2026-06-17 17:53 UTCEPSS rescore
  40. 2026-06-16 17:52 UTCEPSS rescore
  41. 2026-06-16 16:09 UTCVendor advisory
  42. 2026-06-15 17:49 UTCEPSS rescore
  43. 2026-06-15 13:33 UTCVendor advisory
  44. 2026-06-14 10:54 UTCVendor advisory
  45. 2026-06-13 23:00 UTCEPSS rescore
  46. 2026-06-13 09:34 UTCVendor advisory
  47. 2026-06-12 23:12 UTCEPSS rescore
  48. 2026-06-12 23:12 UTCEPSS rescore
  49. 2026-06-12 08:11 UTCVendor advisory
  50. 2026-06-11 14:00 UTCEPSS rescore
  51. 2026-06-11 06:50 UTCVendor advisory
  52. 2026-06-10 22:18 UTCEPSS rescore
  53. 2026-06-10 13:22 UTCEPSS rescore
  54. 2026-06-10 13:22 UTCEPSS rescore
  55. 2026-06-10 05:30 UTCVendor advisory
  56. 2026-06-08 14:17 UTCEPSS rescore
  57. 2026-06-08 14:17 UTCEPSS rescore
  58. 2026-06-07 15:25 UTCEPSS rescore
  59. 2026-06-07 15:25 UTCEPSS rescore
  60. 2026-06-06 13:47 UTCEPSS rescore
  61. 2026-06-06 13:47 UTCEPSS rescore
  62. 2026-06-06 00:08 UTCEG score recompute▼ 2.20
  63. 2026-06-05 22:47 UTCEPSS rescore
  64. 2026-06-05 06:10 UTCEPSS rescore
  65. 2026-06-05 06:10 UTCEPSS rescore
  66. 2026-06-04 13:12 UTCEPSS rescore
  67. 2026-06-04 13:12 UTCEPSS rescore
  68. 2026-06-02 20:13 UTCEPSS rescore
  69. 2026-06-01 13:52 UTCEPSS rescore
  70. 2026-06-01 13:52 UTCEPSS rescore
  71. 2026-05-31 22:30 UTCEPSS rescore
  72. 2026-05-31 22:30 UTCEPSS rescore
  73. 2026-05-31 00:16 UTCEPSS rescore
  74. 2026-05-31 00:16 UTCEPSS rescore
  75. 2026-05-29 13:44 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-42789?
CVE-2026-42789 is a medium vulnerability published on May 27, 2026. Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP publickey (pubkeycert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery. In lib/publickey/src/pubkeycert.erl, pubkeycert:validateextensions/7 contains two…
When was CVE-2026-42789 disclosed?
CVE-2026-42789 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-2026-42789 actively exploited?
CVE-2026-42789 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 74.5% of all scored CVEs.
What is the CVSS score of CVE-2026-42789?
CVE-2026-42789 has a CVSS v3 base score of 4.8 (NVD).
How do I remediate CVE-2026-42789?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42789, 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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