CVE-2026-72854

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-08-20. A secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this weekElevated
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.3Exploit: Elevated riskExposed services: Not assessed

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

msgpack_unpacker_expand_buffer in src/unpack.c, reached through the public msgpack_unpacker_reserve_buffer API, computes its new buffer size using an unchecked size_t addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the addition in the loop condition is unguarded, so a request near SIZE_MAX wraps: the loop condition is already satisfied, the allocation is performed at the small pre-wrap size, and the function returns true. The caller is told the requested capacity was reserved when it was not, so a subsequent write of the requested length overflows the heap buffer. The library's own example/lib_buffer_unpack.c demonstrates the reserve-then-write pattern, and its defensive assert comparing capacity against the request is compiled out under NDEBUG. msgpack-c's own decode entry points do not derive the reservation size from untrusted input, so reaching this requires an integration that passes an attacker-influenced length to the reservation API, such as a length-prefixed streaming transport.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium 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
Severity53% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.2%
EPSS %ILE
4th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

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

August 20, 2026

Last Modified

September 24, 2026

Advisory Details (6)

Auto-updated Aug 20, 2026
No patch confirmed yet.
generic

msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation | Advisories | VulnCheck

https://www.vulncheck.com/advisories/msgpack-c-integer-overflow-in-msgpack-unpacker-expand-buffer-causes-a-false-success-undersized-reservation
generic

GitHub - msgpack/msgpack-c: MessagePack implementation for C and C++ / msgpack.org[C/C++] · GitHub

https://github.com/msgpack/msgpack-c
generic

msgpack-c/example/lib_buffer_unpack.c at c-7.0.1 · msgpack/msgpack-c · GitHub

https://github.com/msgpack/msgpack-c/blob/c-7.0.1/example/lib_buffer_unpack.c
generic

msgpack-c/include/msgpack/unpack.h at c-7.0.1 · msgpack/msgpack-c · GitHub

https://github.com/msgpack/msgpack-c/blob/c-7.0.1/include/msgpack/unpack.h#L219-L223
generic

msgpack-c/src/unpack.c at c-7.0.1 · msgpack/msgpack-c · GitHub

https://github.com/msgpack/msgpack-c/blob/c-7.0.1/src/unpack.c#L429-L502
generic

Integer overflow in msgpack_unpacker_expand_buffer() causes false-success undersized reservation · Issue #1181 · msgpack/msgpack-c · GitHub

https://github.com/msgpack/msgpack-c/issues/1181

Vendor Advisories for CVE-2026-72854(2)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
msgpack-c4.0.0-3 ... 7.0.1-1 (12 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
msgpack-c6.0.1-3, 6.1.0-1, 6.1.0-2, 7.0.1-1
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
msgpack-c6.0.1-3, 6.1.0-1, 6.1.0-2, 7.0.1-1
  • every version on: no fix on record
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 98× 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 141 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-72854?
CVE-2026-72854 is a medium vulnerability published on August 20, 2026. msgpackunpackerexpandbuffer in src/unpack.c, reached through the public msgpackunpackerreservebuffer API, computes its new buffer size using an unchecked sizet addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the…
When was CVE-2026-72854 disclosed?
CVE-2026-72854 was first published on August 20, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-72854 actively exploited?
CVE-2026-72854 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (4th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-72854?
CVE-2026-72854 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-72854?
No fix for CVE-2026-72854 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-72854 are linked in the Vendor Advisories panel on this page.

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