CVE-2026-53720 json
pymonocypher: Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small
published 4mo ago modified 2mo ago also GHSA-8f95-v3jq-cj86 , PYSEC-2026-3000 , EUVD-2026-70531
- cvss
- 5.1
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 7%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi pymonocypher 4.0.2.8
Is CVE-2026-53720 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2mo ago
Exploit prediction
0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 5.1 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N |
| CNA | 4.0 | 5.1 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | pymonocypher | <4.0.2.8 |
4.0.2.8 |
Affected products
- jetperch pymonocypher
Classification
References
-
github.com
/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86
web
-
github.com
/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86
web
- github.com /jetperch/pymonocypher/releases/tag/v4.0.2.8
-
github.com
/jetperch/pymonocypher
package
-
pypi.org
/project/pymonocypher
package
-
github.com
/advisories/GHSA-8f95-v3jq-cj86
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-53720
advisory
Sources
- CVE List CVE-2026-53720
- GitHub Advisory GHSA-8f95-v3jq-cj86
- NVD CVE-2026-53720
- OSV PYSEC-2026-3000
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.