CVE-2026-59876

MEDIUMPre-NVD 4.84.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 87% 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, secondary
Trending — 3 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.

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
4.8(medium)
EPSS
12.6%
KEV
Not listed

Published

July 8, 2026

Last Modified

July 10, 2026

Advisory Details (4)

Auto-updated Jul 9, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 11× 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.

  1. 2026-07-12 10:13 UTCEG score recompute
  2. 2026-07-12 05:46 UTCEPSS rescore
  3. 2026-07-11 11:37 UTCEG score recompute
  4. 2026-07-11 08:27 UTCEPSS rescore
  5. 2026-07-11 08:27 UTCEPSS rescore
  6. 2026-07-10 13:01 UTCEG score recompute
  7. 2026-07-09 19:10 UTCEPSS rescore
  8. 2026-07-09 19:10 UTCEPSS rescore
  9. 2026-07-09 14:24 UTCEG score recompute
  10. 2026-07-08 15:46 UTCEG score recompute
  11. 2026-07-08 15:45 UTCMITRE cvelistV5first tracked

Related CVEs(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 in the National Vulnerability Database on July 8, 2026, with the most recent update on July 10, 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 12.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59876, 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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