CVE-2026-53720

MEDIUMPre-NVD 5.15.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 97% of all CVEs by exploit prediction. 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, secondary
5.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.1Exploit: None knownExposed: 0

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

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
5.1(medium)
EG Risk
28(Track)
EG Risk 28/100SSVC: 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
Severity51% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

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 Patch Available

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 rangeFixed inDependents
pymonocypher0.1.1 ... 4.0.2.7 (19 versions)4.0.2.8—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 4× in last 7d / 15× 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. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 05:37 UTCEG score recompute
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-16 05:15 UTCEPSS rescore
  5. 2026-09-12 03:25 UTCEG score recompute
  6. 2026-09-11 14:53 UTCEPSS rescore
  7. 2026-09-10 09:35 UTCEPSS rescore
  8. 2026-09-09 22:57 UTCEG score recompute
  9. 2026-09-08 22:01 UTCEPSS rescore
  10. 2026-09-07 16:01 UTCEPSS rescore
  11. 2026-09-06 13:47 UTCEPSS rescore
  12. 2026-09-05 22:36 UTCEG score recompute
  13. 2026-09-03 16:33 UTCEG score recompute
  14. 2026-09-03 15:35 UTCEG score recompute▲ 5.10
  15. 2026-09-03 15:34 UTCMITRE cvelistV5CVSS v3 → 5.1 · CVSS v4 → 5.1
  16. 2026-08-01 03:37 UTCEG score recompute
  17. 2026-07-26 12:20 UTCEG score recompute
  18. 2026-07-23 03:19 UTCEG score recompute
  19. 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 vulnerability 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 CVE-2026-53720 disclosed?
CVE-2026-53720 was first published in the National Vulnerability Database on July 9, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53720 actively exploited?
CVE-2026-53720 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 97.4% of all scored CVEs.
What is the CVSS score of CVE-2026-53720?
CVE-2026-53720 has a CVSS v3 base score of 5.1 (NVD).
How do I remediate CVE-2026-53720?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53720, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-53720

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