CVE-2026-54522

MEDIUMNVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under NVD CVSS v3. EPSS exploit probability: 0.2% (12th 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
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: 0.2%CVSS: 5.4Exploit: Elevated riskExposed 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 40/100CISA 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
Severity54% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
12th
KEV
Not listed

CISA SSVCTrack 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). 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 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(2)

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 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 14× in last 7d / 63× 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 143 total refreshes for this CVE.

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

Related CVEs(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 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 0.2% probability of exploitation in the next 30 days (12th 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.

Dependency Blast Radius

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