CVE-2025-8291VulnerabilityPublished 7 Oct 2025Updated 31 Jul 2026

CVE-2025-8291: Python Software Foundation CPython · CWE-1285

Affects Python Software Foundation CPythonSource CVE Database V5

Not known to be exploited · CVSS 4.3 Medium.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score

4.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Python Software Foundation CPython	Affected =3.10.0 =3.11.0 =3.12.0 =3.13.0 =3.14.0	Fixed in–

AI-suggested

The vendor's remediation approach is to maintain the existing behavior but add validation checks on the ZIP64 EOCD Locator offset. Users should monitor official Python Software Foundation advisories for updates or patches addressing this issue.

Description

CVE-2025-8291 is a medium severity vulnerability in the Python Software Foundation's CPython implementation affecting the 'zipfile' module. The issue arises because the module does not properly validate the offset value in the ZIP64 End of Central Directory (EOCD) Locator record and assumes the ZIP64 EOCD record is the previous record in the archive. This discrepancy can cause the 'zipfile' module to handle certain ZIP archives differently than other ZIP implementations. The remediation maintains the original behavior but adds a check to ensure the offset specified in the ZIP64 EOCD Locator record matches the expected value.

Impact

This vulnerability could lead to inconsistent handling of ZIP64 archives by the 'zipfile' module, potentially causing unexpected behavior or logic errors in applications relying on it. There is no direct confidentiality, availability, or privilege escalation impact reported. The CVSS score of 4.3 (medium) reflects limited impact with no known exploits in the wild.

Summary

The vulnerability in CPython's 'zipfile' module involves improper validation of the ZIP64 EOCD Locator record offset. Instead of using the offset to locate the ZIP64 EOCD record, the module assumes it is the previous record in the ZIP archive. This can be exploited to craft ZIP archives that behave inconsistently when processed by the 'zipfile' module compared to other ZIP tools. The fix preserves the original behavior but adds validation to confirm the offset matches the expected location, mitigating potential abuse.

CWE-1285Improper Validation of Specified Index, Position, or Offset in Input (opens in a new tab)
Base weakness
The product receives input that is expected to specify an index, position, or offset into an indexable resource such as a buffer or file, but it does not validate or incorrectly validates that the specified index/position/offset has the required properties.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Aug 2026, 15:00 UTC

WeaknessesCWE-1285

Technical details

References

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