CVE-2026-53720

MEDIUMPre-NVD 5.15.1
EchelonGraph scoreMEDIUM confidence

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

This medium-severity CVE scores 5.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (6th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
5.1EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

pymonocypher uses cython to wrap the Monocypher C library. Prior to version 4.0.2.8, the argon2i_32 implementation does not check the nb_blocks size. If the caller does not provide a sufficiently large buffer based on the API contract, then argon2i_32 will write past the end of the buffer and possibly corrupt the heap. This issue has been patched in version 4.0.2.8.

CVSS v3
5.1
EG Score
5.1MEDIUMmedium confidence
EG Risk
23
EG Risk 23/100

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 (value × EchelonGraph’s weight)
Severity51% × 45%
The EG Score, 5.1 of 10.
Exploitation0.2% × 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
0.2%
EPSS %ILE
6th
KEV
Not listed

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

July 9, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Sep 3, 2026
Patch available. Sources: github, github_commit, github_release.
GitHub release Patch Available

4.0.2.8

Patch available: jetperch/pymonocypher v4.0.2.8

https://github.com/jetperch/pymonocypher/releases/tag/v4.0.2.8
GitHub commit

commit 90ff5b13b13b (jetperch/pymonocypher)

Fix landed in jetperch/pymonocypher commit 90ff5b13b13b — awaiting tagged release

https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86
GitHub advisoryMentions a patch (unverified)

Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small · Advisory · jetperch/pymonocypher · GitHub

Affected: 4.0.2.8, which now verifies that nb_blocks is large enough. See

https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86

Vendor Advisories for CVE-2026-53720(1)

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

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
pymonocypher0.1.1 ... 4.0.2.7 (19 versions)
  • every version up to 4.0.2.8: fixed in 4.0.2.8
—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 33× 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.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  3. 2026-10-12 15:57 UTCEG score recompute
  4. 2026-10-11 19:40 UTCEG score recompute
  5. 2026-10-11 16:55 UTCEG score recompute
  6. 2026-10-11 14:18 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  10. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  12. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  13. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  14. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  15. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  16. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  17. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  18. 2026-10-01 16:03 UTCEG score recompute
  19. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  20. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  22. 2026-09-28 10:54 UTCEG score recompute
  23. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  24. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  25. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.2% · 6th percentile
Show 23 more
  1. 2026-09-24 11:40 UTCEG score recompute
  2. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  3. 2026-09-23 05:59 UTCEG score recompute
  4. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  5. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  6. 2026-09-18 05:37 UTCEG score recompute
  7. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  8. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  9. 2026-09-12 03:25 UTCEG score recompute
  10. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  11. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  12. 2026-09-09 22:57 UTCEG score recompute
  13. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  14. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  15. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  16. 2026-09-05 22:36 UTCEG score recompute
  17. 2026-09-03 16:33 UTCEG score recompute
  18. 2026-09-03 15:35 UTCEG score recomputeFirst assessed: 5.1 MEDIUM
  19. 2026-09-03 15:34 UTCMITRE cvelistV5CVSS v3 → 5.1 · CVSS v4 → 5.1
  20. 2026-08-01 03:37 UTCEG score recompute
  21. 2026-07-26 12:20 UTCEG score recompute
  22. 2026-07-23 03:19 UTCEG score recompute
  23. 2026-07-09 13:45 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-53720?
CVE-2026-53720 is a medium-severity vulnerability; its CVE record was published on July 9, 2026. pymonocypher uses cython to wrap the Monocypher C library. Prior to version 4.0.2.8, the argon2i32 implementation does not check the nbblocks size. If the caller does not provide a sufficiently large buffer based on the API contract, then argon2i_32 will write past the end of the buffer and…
When was the CVE record for CVE-2026-53720 published?
The CVE record for CVE-2026-53720 was published on July 9, 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 September 9, 2026; the record at its source may have been updated since.
Is CVE-2026-53720 actively exploited?
CVE-2026-53720 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (6th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-53720?
CVE-2026-53720 has a CVSS base score of 5.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-53720?
A fix for CVE-2026-53720 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-53720 are linked in the Vendor Advisories panel on this page.

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