CVE-2026-42789

MEDIUMNVD 4.88.0▲
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.0 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 76% 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: adp:redhat-sadp, epss
Trending — 5 sources updated this week
4.8
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 26.2.5.21, 27.3.4.12, 28.5.0.1, and 29.0.1 corresponding to public_key from 0.22 before 1.15.1.7, 1.17.1.3, 1.20.3.1, and 1.21.1.

CVSS v3
4.8
EG Score
8.0(medium)
EPSS
24.2%
KEV
Not listed

Published

May 27, 2026

Last Modified

July 15, 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.

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 58× 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 114 total refreshes for this CVE.

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

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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 15, 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 24.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42789?
CVE-2026-42789 has a CVSS v3 base score of 4.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.0.
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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