CVE-2026-59876

MEDIUMNVD 4.84.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.8 under NVD CVSS v3. EPSS exploit probability: 0.3% (26th percentile of EPSS-scored CVEs). 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
4.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 4.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key __proto__ to change the prototype of the returned map object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.

CVSS v3
4.8
EG Score
4.8MEDIUMmedium confidence
EG Risk
22
EG Risk 22/100CISA SSVC

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%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
26th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 8, 2026

Last Modified

July 13, 2026

Advisory Details (4)

Auto-updated Jul 9, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
githubMentions a patch (unverified)

Text Format string map parsing can mutate returned map object prototype · Advisory · protobufjs/protobuf.js · GitHub

https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934
github_release Patch Available

protobufjs: v8.6.5

Patch available: protobufjs/protobuf.js protobufjs-v8.6.5

https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5
github_pr Patch Available

fix: Use own-property semantics for internal maps

Patch available: protobufjs/protobuf.js protobufjs-cli-v2.5.6 (PR #2335 merged 2026-06-21)

https://github.com/protobufjs/protobuf.js/pull/2335
github_commit Patch Available

commit 9f97fe413072 (protobufjs/protobuf.js)

Patch available: protobufjs/protobuf.js protobufjs-cli-v2.5.6 (contains commit 9f97fe413072)

https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8

Vendor Advisories for CVE-2026-59876(1)

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

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
protobufjs—
  • 8.2.0 up to 8.6.5: fixed in 8.6.5
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 33× 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 136 total refreshes for this CVE.

  1. 2026-10-10 20:00 UTCEPSS rescore
  2. 2026-10-09 20:07 UTCEPSS rescore
  3. 2026-10-08 17:13 UTCEPSS rescore
  4. 2026-10-07 23:48 UTCEPSS rescore
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  11. 2026-10-01 16:12 UTCEG score recompute
  12. 2026-09-30 15:03 UTCEPSS rescore
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  15. 2026-09-28 13:23 UTCEG score recompute
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  1. 2026-09-16 14:08 UTCEPSS rescore
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  8. 2026-09-11 14:53 UTCEPSS rescore
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  13. 2026-09-05 22:48 UTCEG score recompute
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  22. 2026-08-27 21:50 UTCEG score recompute
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  26. 2026-08-25 13:49 UTCEPSS rescore
  27. 2026-08-24 20:39 UTCEG score recompute
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  35. 2026-08-19 17:04 UTCEPSS rescore
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  37. 2026-08-18 13:48 UTCEPSS rescore
  38. 2026-08-18 06:18 UTCEG score recompute
  39. 2026-08-17 13:47 UTCEPSS rescore
  40. 2026-08-17 07:01 UTCEG score recompute
  41. 2026-08-16 14:56 UTCEPSS rescore
  42. 2026-08-16 08:26 UTCEG score recompute
  43. 2026-08-16 02:14 UTCEPSS rescore
  44. 2026-08-15 09:51 UTCEG score recompute
  45. 2026-08-15 01:30 UTCEPSS rescore
  46. 2026-08-14 11:15 UTCEG score recompute
  47. 2026-08-13 22:00 UTCEPSS rescore
  48. 2026-08-12 14:05 UTCEG score recompute
  49. 2026-08-12 13:51 UTCEPSS rescore
  50. 2026-08-11 15:26 UTCEG score recompute
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  58. 2026-08-06 13:47 UTCEPSS rescore
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  60. 2026-08-05 19:17 UTCEPSS rescore
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  74. 2026-07-29 08:18 UTCEG score recompute
  75. 2026-07-28 15:37 UTCEPSS rescore

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-59876?
CVE-2026-59876 is a medium vulnerability published on July 8, 2026. protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key proto to change the prototype of the returned map object instead of…
When was CVE-2026-59876 disclosed?
CVE-2026-59876 was first published on July 8, 2026, with the most recent update on July 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59876 actively exploited?
CVE-2026-59876 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (26th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-59876?
CVE-2026-59876 has a CVSS v3 base score of 4.8 (NVD).
How do I remediate CVE-2026-59876?
A fix for CVE-2026-59876 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-59876 are linked in the Vendor Advisories panel on this page.

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