CVE-2026-72854

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreHIGH 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%CVSS: 5.3Exploit: Elevated riskExposed: 0

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

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
5.3(high)
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
Severity53% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
2%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 20, 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(1)

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 rangeFixed inDependents
msgpack-c4.0.0-3 ... 7.0.1-1 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
msgpack-c6.0.1-3, 6.1.0-1, 6.1.0-2, 7.0.1-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
msgpack-c6.0.1-3, 6.1.0-1, 6.1.0-2, 7.0.1-1——

Weakness Classification(2)

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 23× in last 7d / 85× 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. 2026-09-19 20:29 UTCVendor advisory
  2. 2026-09-19 20:29 UTCGHSA enrichment
  3. 2026-09-18 21:39 UTCEG score recompute
  4. 2026-09-18 21:39 UTCVendor advisory
  5. 2026-09-18 21:39 UTCGHSA enrichment
  6. 2026-09-18 19:28 UTCEPSS rescore
  7. 2026-09-17 21:19 UTCEG score recompute
  8. 2026-09-17 21:19 UTCVendor advisory
  9. 2026-09-17 21:19 UTCGHSA enrichment
  10. 2026-09-16 20:02 UTCEG score recompute
  11. 2026-09-16 20:02 UTCVendor advisory
  12. 2026-09-16 20:01 UTCGHSA enrichment
  13. 2026-09-16 14:08 UTCEPSS rescore
  14. 2026-09-16 05:15 UTCEPSS rescore
  15. 2026-09-15 18:48 UTCEG score recompute
  16. 2026-09-15 18:48 UTCVendor advisory
  17. 2026-09-15 18:48 UTCGHSA enrichment
  18. 2026-09-15 03:12 UTCEPSS rescore
  19. 2026-09-14 19:58 UTCVendor advisory
  20. 2026-09-14 19:58 UTCGHSA enrichment
  21. 2026-09-13 21:08 UTCEG score recompute
  22. 2026-09-13 21:08 UTCVendor advisory
  23. 2026-09-13 21:08 UTCGHSA enrichment
  24. 2026-09-12 22:18 UTCEG score recompute
  25. 2026-09-12 22:18 UTCVendor advisory
Show 64 more
  1. 2026-09-12 22:18 UTCGHSA enrichment
  2. 2026-09-12 15:02 UTCEPSS rescore
  3. 2026-09-11 23:28 UTCEG score recompute
  4. 2026-09-11 23:28 UTCVendor advisory
  5. 2026-09-11 23:28 UTCGHSA enrichment
  6. 2026-09-11 14:53 UTCEPSS rescore
  7. 2026-09-11 00:18 UTCEG score recompute
  8. 2026-09-11 00:18 UTCGHSA enrichment
  9. 2026-09-10 09:35 UTCEPSS rescore
  10. 2026-09-10 00:49 UTCGHSA enrichment
  11. 2026-09-09 01:55 UTCEG score recompute
  12. 2026-09-09 01:55 UTCVendor advisory
  13. 2026-09-09 01:55 UTCGHSA enrichment
  14. 2026-09-08 22:01 UTCEPSS rescore
  15. 2026-09-07 21:27 UTCVendor advisory
  16. 2026-09-07 21:27 UTCGHSA enrichment
  17. 2026-09-06 22:37 UTCEG score recompute
  18. 2026-09-06 22:37 UTCGHSA enrichment
  19. 2026-09-06 13:48 UTCEPSS rescore
  20. 2026-09-05 23:48 UTCEG score recompute
  21. 2026-09-05 23:48 UTCGHSA enrichment
  22. 2026-09-05 00:58 UTCEG score recompute
  23. 2026-09-05 00:58 UTCGHSA enrichment
  24. 2026-09-04 02:04 UTCGHSA enrichment
  25. 2026-09-03 03:13 UTCGHSA enrichment
  26. 2026-09-02 04:20 UTCEG score recompute
  27. 2026-09-02 04:20 UTCGHSA enrichment
  28. 2026-09-01 13:54 UTCEPSS rescore
  29. 2026-09-01 05:30 UTCEG score recompute
  30. 2026-09-01 05:30 UTCGHSA enrichment
  31. 2026-09-01 04:40 UTCEPSS rescore
  32. 2026-09-01 04:40 UTCEPSS rescore
  33. 2026-08-31 06:33 UTCEG score recompute
  34. 2026-08-31 06:33 UTCGHSA enrichment
  35. 2026-08-30 19:18 UTCEPSS rescore
  36. 2026-08-30 19:17 UTCEPSS rescore
  37. 2026-08-30 07:44 UTCGHSA enrichment
  38. 2026-08-29 08:54 UTCEG score recompute
  39. 2026-08-29 08:54 UTCGHSA enrichment
  40. 2026-08-28 21:42 UTCEPSS rescore
  41. 2026-08-28 10:04 UTCEG score recompute
  42. 2026-08-28 10:04 UTCGHSA enrichment
  43. 2026-08-27 14:25 UTCEPSS rescore
  44. 2026-08-27 11:14 UTCEG score recompute
  45. 2026-08-27 11:14 UTCGHSA enrichment
  46. 2026-08-26 14:47 UTCEPSS rescore
  47. 2026-08-26 12:24 UTCEG score recompute
  48. 2026-08-26 12:24 UTCGHSA enrichment
  49. 2026-08-25 13:49 UTCEPSS rescore
  50. 2026-08-25 13:28 UTCGHSA enrichment
  51. 2026-08-24 14:39 UTCEG score recompute
  52. 2026-08-24 14:39 UTCGHSA enrichment
  53. 2026-08-23 15:47 UTCEG score recompute
  54. 2026-08-23 15:47 UTCGHSA enrichment
  55. 2026-08-23 00:19 UTCEPSS rescore
  56. 2026-08-22 16:58 UTCEG score recompute
  57. 2026-08-22 16:58 UTCGHSA enrichment
  58. 2026-08-21 23:49 UTCEPSS rescore
  59. 2026-08-21 18:08 UTCEG score recompute
  60. 2026-08-21 18:08 UTCGHSA enrichment
  61. 2026-08-20 19:18 UTCEG score recompute
  62. 2026-08-20 19:12 UTCEG score recompute
  63. 2026-08-20 18:32 UTCEG score recompute
  64. 2026-08-20 18:31 UTCMITRE cvelistV5first tracked

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 in the National Vulnerability Database on August 20, 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% probability of exploitation in the next 30 days, which ranks it in the top 98.4% of all scored CVEs.
What is the CVSS score of CVE-2026-72854?
CVE-2026-72854 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-72854?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-72854, 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

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