CVE-2023-28638

HIGHNVD 7.07.0
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 7.0 under NVD CVSS v3. EPSS exploit probability: 0.5% (45th 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
7.0EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.0Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Snappier is a high performance C# implementation of the Snappy compression algorithm. This is a buffer overrun vulnerability that can affect any user of Snappier 1.1.0. In this release, much of the code was rewritten to use byte references rather than pointers to pinned buffers. This change generally improves performance and reduces workload on the garbage collector. However, when the garbage collector performs compaction and rearranges memory, it must update any byte references on the stack to refer to the updated location. The .NET garbage collector can only update these byte references if they still point within the buffer or to a point one byte past the end of the buffer. If they point outside this area, the buffer itself may be moved while the byte reference stays the same. There are several places in 1.1.0 where byte references very briefly point outside the valid areas of buffers. These are at locations in the code being used for buffer range checks. While the invalid references are never dereferenced directly, if a GC compaction were to occur during the brief window when they are on the stack then it could invalidate the buffer range check and allow other operations to overrun the buffer. This should be very difficult for an attacker to trigger intentionally. It would require a repetitive bulk attack with the hope that a GC compaction would occur at precisely the right moment during one of the requests. However, one of the range checks with this problem is a check based on input data in the decompression buffer, meaning malformed input data could be used to increase the chance of success. Note that any resulting buffer overrun is likely to cause access to protected memory, which will then cause an exception and the process to be terminated. Therefore, the most likely result of an attack is a denial of service. This issue has been patched in release 1.1.1. Users are advised to upgrade. Users unable to upgrade may pin buffers to a fixed location before using them for compression or decompression to mitigate some, but not all, of these cases. At least one temporary decompression buffer is internal to the library and never pinned.

CVSS v3
7.0
EG Score
7.0HIGHmedium confidence
EG Risk
32
EG Risk 32/100

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)
Severity70% × 45%
Impact severity (EG Severity): CVSS 7.0 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (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
0.5%
EPSS %ILE
45th
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 (7.0): severity, escalated by confirmed exploitation. This CVE's 7.0 is its impact severity (EG Severity), not escalated.

EG Severity
7.0 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-20). 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 every mission impact level.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: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

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

Exploitation none (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.

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

March 27, 2023

Last Modified

November 21, 2024

References (2)

Affected Packages

(1 across 1 ecosystem)
NuGet(1)
PackageVulnerable rangeFix by version rangeDependents
Snappier1.1.0
  • 1.1.0 up to 1.1.1: fixed in 1.1.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 35× 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 92 of 198 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. 8 repeat rows among the latest 100 are merged into the row they repeat. The 106 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-23 16:29 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  2. 2026-10-22 16:31 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  3. 2026-10-21 16:29 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  4. 2026-10-21 04:21 UTCEG score recompute
  5. 2026-10-20 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  6. 2026-10-19 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  7. 2026-10-18 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  8. 2026-10-18 08:07 UTCEG score recompute
  9. 2026-10-17 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  10. 2026-10-16 16:35 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  11. 2026-10-15 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  12. 2026-10-14 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  13. 2026-10-14 16:24 UTCOSV refresh
  14. 2026-10-13 16:29 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  15. 2026-10-12 18:29 UTCEG score recompute
  16. 2026-10-12 16:30 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  17. 2026-10-11 21:55 UTCEG score recompute
  18. 2026-10-11 13:45 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  19. 2026-10-10 19:57 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  20. 2026-10-09 20:05 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  21. 2026-10-08 17:06 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  22. 2026-10-07 23:45 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  23. 2026-10-06 15:15 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  24. 2026-10-05 17:41 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  25. 2026-10-04 23:20 UTCEPSS rescoreEPSS 0.6% · 44th percentile
Show 67 more
  1. 2026-10-03 14:23 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  2. 2026-10-02 16:23 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  3. 2026-10-01 19:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  4. 2026-09-30 16:20 UTCEG score recompute
  5. 2026-09-30 15:01 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  6. 2026-09-29 15:16 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  7. 2026-09-28 13:49 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  8. 2026-09-27 13:42 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  9. 2026-09-26 00:22 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  10. 2026-09-24 14:01 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  11. 2026-09-23 17:17 UTCOSV refresh
  12. 2026-09-23 13:45 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  13. 2026-09-22 14:45 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  14. 2026-09-20 20:14 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  15. 2026-09-16 14:05 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  16. 2026-09-13 16:44 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  17. 2026-09-12 14:58 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  18. 2026-09-11 14:50 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  19. 2026-09-11 09:34 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  20. 2026-09-08 21:57 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  21. 2026-09-07 15:59 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  22. 2026-09-06 13:45 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  23. 2026-09-05 15:25 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  24. 2026-09-04 13:58 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  25. 2026-09-04 11:59 UTCOSV refresh
  26. 2026-09-04 05:04 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  27. 2026-09-02 14:09 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  28. 2026-09-01 13:51 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  29. 2026-08-30 19:15 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  30. 2026-08-30 01:19 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  31. 2026-08-28 21:38 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  32. 2026-08-27 14:23 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  33. 2026-08-26 14:43 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  34. 2026-08-25 13:46 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  35. 2026-08-24 14:14 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  36. 2026-08-23 00:17 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  37. 2026-08-21 23:46 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  38. 2026-08-20 22:53 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  39. 2026-08-19 17:02 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  40. 2026-08-18 13:46 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  41. 2026-08-17 23:00 UTCOSV refresh
  42. 2026-08-17 13:44 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  43. 2026-08-16 14:53 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  44. 2026-08-16 02:12 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  45. 2026-08-15 01:28 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  46. 2026-08-13 21:58 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  47. 2026-08-12 13:48 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  48. 2026-08-11 13:39 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  49. 2026-08-09 13:44 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  50. 2026-08-08 16:34 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  51. 2026-08-07 16:24 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  52. 2026-08-06 13:44 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  53. 2026-08-05 19:15 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  54. 2026-08-04 15:07 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  55. 2026-08-04 10:35 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  56. 2026-08-03 10:34 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  57. 2026-08-02 17:57 UTCOSV refresh
  58. 2026-08-02 02:24 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  59. 2026-08-01 04:13 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  60. 2026-07-30 16:26 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  61. 2026-07-30 01:28 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  62. 2026-07-28 15:34 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  63. 2026-07-27 14:10 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  64. 2026-07-26 14:52 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  65. 2026-07-25 14:16 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  66. 2026-07-24 14:15 UTCEPSS rescoreEPSS 0.6% · 42nd percentile
  67. 2026-07-23 14:16 UTCEPSS rescoreEPSS 0.6% · 42nd percentile

Related CVEs(same product + same CWE)

Same product

1 shown

NuGet:Snappier

Frequently asked(5)

What is CVE-2023-28638?
CVE-2023-28638 is a high-severity vulnerability; its CVE record was published on March 27, 2023. Snappier is a high performance C# implementation of the Snappy compression algorithm. This is a buffer overrun vulnerability that can affect any user of Snappier 1.1.0. In this release, much of the code was rewritten to use byte references rather than pointers to pinned buffers. This change…
When was the CVE record for CVE-2023-28638 published?
The CVE record for CVE-2023-28638 was published on March 27, 2023. 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 November 21, 2024; the record at its source may have been updated since.
Is CVE-2023-28638 actively exploited?
CVE-2023-28638 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (45th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2023-28638?
CVE-2023-28638 has a CVSS v3 base score of 7.0 (NVD).
How do I remediate CVE-2023-28638?
A fix for CVE-2023-28638 is available: update to the fixed version the vendor names in its advisory.

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