CVE-2026-54522

MEDIUMNVD 5.45.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This medium-severity CVE scores 5.4 under NVD CVSS v3. EPSS exploit probability: 0.2% (13th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Trending — 4 sources updated this weekElevated

Also known asEUVD-2026-51235 (ENISA EUVD) · GHSA-4mrv-5p47-p938 (GitHub Security Advisories)Source: ENISA EUVD

5.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.4Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
5.4MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity54% × 45%
Impact severity (EG Severity): CVSS 5.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
13th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.4): severity, escalated by confirmed exploitation. This CVE's 5.4 is its impact severity (EG Severity), not escalated.

EG Severity
5.4 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

July 30, 2026

Last Modified

October 23, 2026

Advisory Details (2)

Auto-updated Aug 5, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

[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(2)

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

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
rubygemsmsgpack @ 1.8.2 (fixes <= 1.8.1)—ghsa

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

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-msgpack1.1.0-2 ... 1.8.4-1 (8 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-msgpack1.4.2-2 ... 1.8.5-1 (7 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-msgpack1.7.2-1.1, 1.8.0-1, 1.8.3-1, 1.8.4-1, 1.8.5-1
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-msgpack1.7.2-1.1, 1.8.0-1
  • every version up to 1.8.3-1: fixed in 1.8.3-1
—
RubyGems(1)
PackageVulnerable rangeFix by version rangeDependents
msgpack0.0.1 ... 1.8.1 (93 versions)
  • every version up to 1.8.2: fixed in 1.8.2
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 48× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 187 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 87 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  2. 2026-11-01 07:44 UTCGHSA enrichmentGHSA-4mrv-5p47-p938 · GitHub severity LOW
  3. 2026-11-01 07:44 UTCEG score recompute
  4. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  6. 2026-10-29 16:34 UTCEG score recompute
  7. 2026-10-29 16:34 UTCVendor advisory
  8. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  9. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  10. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  12. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  13. 2026-10-25 14:19 UTCEG score recompute
  14. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  15. 2026-10-23 22:31 UTCEG score recompute
  16. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  17. 2026-10-22 21:20 UTCEG score recompute
  18. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  19. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  20. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  21. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  22. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  23. 2026-10-18 03:30 UTCEG score recompute
  24. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  25. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.2% · 12th percentile
Show 75 more
  1. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  2. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  3. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  5. 2026-10-12 15:56 UTCEG score recompute
  6. 2026-10-11 19:39 UTCEG score recompute
  7. 2026-10-11 16:54 UTCEG score recompute
  8. 2026-10-11 14:18 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  12. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  13. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  14. 2026-10-06 23:52 UTCEG score recompute
  15. 2026-10-06 23:52 UTCVendor advisory
  16. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  17. 2026-10-05 20:00 UTCEG score recompute
  18. 2026-10-05 20:00 UTCVendor advisory
  19. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  20. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  21. 2026-10-04 06:38 UTCEG score recompute
  22. 2026-10-04 06:38 UTCVendor advisory
  23. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  24. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  25. 2026-10-02 16:57 UTCEG score recompute
  26. 2026-10-02 16:57 UTCVendor advisory
  27. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  28. 2026-10-01 02:54 UTCEG score recompute
  29. 2026-10-01 02:54 UTCVendor advisory
  30. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  31. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  32. 2026-09-29 06:53 UTCEG score recompute
  33. 2026-09-29 06:53 UTCVendor advisory
  34. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  35. 2026-09-27 19:00 UTCEG score recompute
  36. 2026-09-27 19:00 UTCVendor advisory
  37. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  38. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  39. 2026-09-25 04:56 UTCEG score recompute
  40. 2026-09-25 04:56 UTCVendor advisory
  41. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  42. 2026-09-23 21:29 UTCEG score recompute
  43. 2026-09-23 21:29 UTCVendor advisory
  44. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  45. 2026-09-22 15:13 UTCEG score recompute
  46. 2026-09-22 15:13 UTCVendor advisory
  47. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  48. 2026-09-20 04:27 UTCEG score recompute
  49. 2026-09-20 04:27 UTCVendor advisory
  50. 2026-09-19 04:15 UTCEG score recompute
  51. 2026-09-19 04:15 UTCVendor advisory
  52. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  53. 2026-09-18 01:22 UTCEG score recompute
  54. 2026-09-18 01:22 UTCVendor advisory
  55. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  56. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  57. 2026-09-16 11:43 UTCEG score recompute
  58. 2026-09-16 11:43 UTCVendor advisory
  59. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  60. 2026-09-15 08:49 UTCEG score recompute
  61. 2026-09-15 08:49 UTCVendor advisory
  62. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  63. 2026-09-14 08:39 UTCEG score recompute
  64. 2026-09-14 08:39 UTCVendor advisory
  65. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  66. 2026-09-13 08:32 UTCEG score recompute
  67. 2026-09-13 08:32 UTCVendor advisory
  68. 2026-09-12 08:25 UTCEG score recompute
  69. 2026-09-12 08:25 UTCVendor advisory
  70. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  71. 2026-09-11 07:26 UTCEG score recompute
  72. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  73. 2026-09-09 07:13 UTCEG score recompute
  74. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  75. 2026-09-07 19:50 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54522?
CVE-2026-54522 is a medium-severity vulnerability; its CVE record was 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 rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a…
When was the CVE record for CVE-2026-54522 published?
The CVE record for CVE-2026-54522 was published on July 30, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 23, 2026; the record at its source may have been updated since.
Is CVE-2026-54522 actively exploited?
CVE-2026-54522 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (13th percentile of EPSS-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?
A fix for CVE-2026-54522 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-54522 are linked in the Vendor Advisories panel on this page.

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