CVE-2026-54522

MEDIUMNVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 96% 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 — 3 sources updated this weekElevated
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: Elevated riskExposed: 0

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

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.

CVSS v3
5.4
EG Score
5.4(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity54% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
4%
KEV
Not listed

Published

July 30, 2026

Last Modified

August 5, 2026

Advisory Details (2)

Auto-updated Aug 5, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available

[DFVULN-839] Use-After-Free in MessagePack::Buffer#clear Enables Cross-Buffer Disclosure · Advisory · msgpack/msgpack-ruby · GitHub

https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938
github_commit

commit 5627d71606b5 (msgpack/msgpack-ruby)

Fix landed in msgpack/msgpack-ruby commit 5627d71606b5 — awaiting tagged release

https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90

Vendor Advisories for CVE-2026-54522(1)

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

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
ruby-msgpack1.1.0-2 ... 1.8.4-1 (8 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
ruby-msgpack1.4.2-2 ... 1.8.4-1 (6 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
ruby-msgpack1.7.2-1.1, 1.8.0-1, 1.8.3-1, 1.8.4-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
ruby-msgpack1.7.2-1.1, 1.8.0-11.8.3-1—
RubyGems(1)
PackageVulnerable rangeFixed inDependents
msgpack0.0.1 ... 1.8.1 (93 versions)1.8.2—

Weakness Classification(1)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 20× in last 7d / 46× 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. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-20 22:10 UTCVendor advisory
  3. 2026-08-19 21:52 UTCEG score recompute
  4. 2026-08-19 21:52 UTCVendor advisory
  5. 2026-08-19 17:04 UTCEPSS rescore
  6. 2026-08-18 21:45 UTCEG score recompute
  7. 2026-08-18 21:45 UTCVendor advisory
  8. 2026-08-18 13:48 UTCEPSS rescore
  9. 2026-08-17 21:11 UTCEG score recompute
  10. 2026-08-17 21:11 UTCVendor advisory
  11. 2026-08-17 13:47 UTCEPSS rescore
  12. 2026-08-16 21:05 UTCEG score recompute
  13. 2026-08-16 21:05 UTCVendor advisory
  14. 2026-08-16 14:56 UTCEPSS rescore
  15. 2026-08-16 02:14 UTCEPSS rescore
  16. 2026-08-15 20:58 UTCEG score recompute
  17. 2026-08-15 20:58 UTCVendor advisory
  18. 2026-08-15 01:30 UTCEPSS rescore
  19. 2026-08-14 20:51 UTCEG score recompute
  20. 2026-08-14 20:51 UTCVendor advisory
  21. 2026-08-13 22:00 UTCEPSS rescore
  22. 2026-08-12 20:37 UTCEG score recompute
  23. 2026-08-12 13:51 UTCEPSS rescore
  24. 2026-08-11 20:31 UTCEG score recompute
  25. 2026-08-11 00:00 UTCEPSS rescore
Show 21 more
  1. 2026-08-09 20:17 UTCEG score recompute
  2. 2026-08-09 13:46 UTCEPSS rescore
  3. 2026-08-08 20:11 UTCEG score recompute
  4. 2026-08-08 16:37 UTCEPSS rescore
  5. 2026-08-07 20:04 UTCEG score recompute
  6. 2026-08-06 19:58 UTCEG score recompute
  7. 2026-08-06 13:47 UTCEPSS rescore
  8. 2026-08-05 19:51 UTCEG score recompute▲ 3.30
  9. 2026-08-05 19:51 UTCNVD updateCVSS v3 → 5.4 · severity → MEDIUM
  10. 2026-08-05 19:17 UTCEPSS rescore
  11. 2026-08-05 10:06 UTCEG score recompute
  12. 2026-08-04 10:39 UTCEPSS rescore
  13. 2026-08-03 10:36 UTCEPSS rescore
  14. 2026-08-02 14:49 UTCEG score recompute
  15. 2026-08-02 02:27 UTCEPSS rescore
  16. 2026-08-01 04:16 UTCEPSS rescore
  17. 2026-07-30 19:31 UTCEG score recompute
  18. 2026-07-30 18:02 UTCEG score recompute
  19. 2026-07-30 17:24 UTCEG score recompute
  20. 2026-07-30 16:48 UTCEG score recompute
  21. 2026-07-30 16:46 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-54522?
CVE-2026-54522 is a medium vulnerability published on July 30, 2026. MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmemlast, rmemend, and rmemowner stale after msgpackbuffershift_chunk returns an rmem page to the shared pool, allowing a subsequent…
When was CVE-2026-54522 disclosed?
CVE-2026-54522 was first published in the National Vulnerability Database on July 30, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54522 actively exploited?
CVE-2026-54522 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 96.5% of all scored CVEs.
What is the CVSS score of CVE-2026-54522?
CVE-2026-54522 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-54522?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54522, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-54522

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