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 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
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
26%
KEV
Not listed

Published

May 27, 2026

Last Modified

August 14, 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(2)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhaterlang-0:23.3.4.18-2.el8ost2026-08-13redhat
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.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
erlang1:23.2.6+dfsg-1 ... 1:29.0~rc3+dfsg-4 (117 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
erlang1:25.2.3+dfsg-1 ... 1:29.0~rc3+dfsg-4 (78 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
erlang1:27.3.4.1+dfsg-1, 1:27.3.4.1+dfsg-1+deb13u1, 1:27.3.4.1+dfsg-1+deb13u21:27.3.4.1+dfsg-1+deb13u3—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
erlang1:27.3.4.1+dfsg-1 ... 1:27.3.4.9+dfsg-1 (14 versions)1:27.3.4.12+dfsg-1—

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 9× in last 7d / 35× 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 194 total refreshes for this CVE.

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

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 August 14, 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 74.0% 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.

Dependency Blast Radius

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