CVE-2021-3177
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Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python…
rank 39 = 6 + 25 + 0 + 8 + 0
rank@v1 · scheduled
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.23293 · without this subject the record ranks 33
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 9.8, from NVD · without this subject the record ranks 14
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 39
How much of the world it touches
NVD CPE configurations
12 products in the CPE ranges · without this subject the record ranks 31
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 39
$1.16M = $4.99M incident cost x 1 exposure x 0.23293 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
This record is one instance of CWE-120, buffer copy without checking size of input ('classic buffer overflow'). The index holds 4490 prior instances of this class, 24 KEV-listed. The nearest of its KEV-listed records are drawn beside this. taxonomy@v1
Check a version against this record
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Harm, if it fires from the vector and the weakness
Written for the ticket you're about to file.
CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Nothing observed in held sources.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 12 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely. receipt
NVD's analysis a second authority
- severity
- 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- weakness
- CWE-120
- affected versions
- python >= 3.6.0 <= 3.6.12; python >= 3.7.0 <= 3.7.9; python >= 3.8.0 <= 3.8.7; and 9 more, listed in full below
- also scored by
- 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
check it yourself bugs.python.org github.com python-security.readthedocs.io lists.fedoraproject.org lists.fedoraproject.org security.gentoo.org +14 morereceipt
Dated events
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 65 observations
65 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The full biography
Exploit probability more than doubled between 2025-03-28 and 2025-03-29 (0.00032 → 0.00265) and the record had been public for 5 years, 6 months when this index was last written.
The pattern, elsewhere
This record is one instance of CWE-120, buffer copy without checking size of input ('classic buffer overflow'). The index holds 4490 prior instances of this class, 24 KEV-listed. The nearest of its KEV-listed records are drawn beside this. [email protected]
"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1
4490 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.
No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.
Siblings and hubs
Records related to this one
None. No alias set, and nothing in the corpus cites this identifier or shares its product family within 60 days.
Browse the index from here
These are index-wide views, not findings about CVE-2021-3177.
What usually comes next
Everything above needs no account. What is below is work: assembling it, scoping it to your estate, watching it, and handing it to someone else.