What is the CVSS score of CVE-2025-12781?

CVE-2025-12781 has a CVSS 3.1 base score of 5.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for CVE-2025-12781?

Yes, a public proof-of-concept exploit is available for CVE-2025-12781. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2025-12781?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Python CVE-2025-12781

MEDIUM

Incorrect Type Conversion or Cast (CWE-704)

2026-01-21 cna@python.org

Python Red Hat Suse

5.3

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-704 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Correct type conversion
Impact	CVSS 5.3 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Public exploit/POC available.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to compromise the affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

RemediationAI

A vendor patch is available — apply it immediately. Restrict network access to the affected service where possible.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Classified as CWE-704 (Incorrect Type Conversion or Cast). Affects Python. When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 5.3 MEDIUM

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

SUSE MEDIUM

Red Hat 5.3 MEDIUM

Primary rating from NVD.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Lifecycle Timeline

PoC Detected

Feb 02, 2026 - 17:25 vuln.today

Public exploit code

Patch released

Feb 02, 2026 - 17:25 nvd

Patch available

CVE Published

Jan 21, 2026 - 20:16 nvd

MEDIUM 5.3

DescriptionCVE.org

When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues.

This behavior can only be insecure if your application uses an alternate base64 alphabet (without "+/"). If your application does not use the "altchars" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet.

The attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python. Users are recommended to mitigate by verifying user-controlled inputs match the base64 alphabet they are expecting or verify that their application would not be affected if the b64decode() functions accepted "+" or "/" outside of altchars.

Executive ViewAI

Why It Matters

CVE-2025-12781 presents moderate security risk rated CVSS 5.3. Exploitation could compromise the security of affected deployments. Proof-of-concept code is publicly available. A patch is available and should be applied during regular vulnerability management.

Business Impact: Low

Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score

0.0%

Top 96% exploitable

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS Vendor

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Low

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +26

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Affected Products (CPE)CVE.org

cpe:2.3:a:python:python:*:*:*:*:*:*:*:*

cpe:2.3:a:python:python:3.15.0:alpha1:*:*:*:*:*:*

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Vendor StatusVendor

SUSE

Severity: Medium

Product	Status
Container suse/sl-micro/6.0/toolbox:13.2-9.73	Affected
Container suse/sl-micro/6.1/baremetal-os-container:2.2.1-7.67 Image SL-Micro-EC2 Image SUSE-Multi-Linux-Manager-Server-EC2-llc Image SUSE-Multi-Linux-Manager-Server-EC2-ltd	Affected
Image SLES15-SP4-HPC-BYOS Image SLES15-SP4-HPC-BYOS-EC2 Image SLES15-SP4-HPC-EC2 Image SLES15-SP4-Hardened-BYOS Image SLES15-SP4-Hardened-BYOS-EC2 Image SLES15-SP4-SAP-BYOS Image SLES15-SP4-SAP-BYOS-EC2 Image SLES15-SP4-SAP-Hardened-BYOS Image SLES15-SP4-SAP-Hardened-BYOS-EC2 Image SLES15-SP5-BYOS-EC2 Image SLES15-SP5-HPC-BYOS-EC2 Image SLES15-SP5-Hardened-BYOS-EC2 Image SLES15-SP5-SAP-BYOS-EC2 Image SLES15-SP5-SAP-Hardened-BYOS-EC2	Affected
Image SLES15-SP7-SAP-BYOS-EC2 Image SLES15-SP7-SAP-Hardened-BYOS-EC2	Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7	Fixed

References

Advisories & patches

PATCH https://github.com/python/cpython/commit/13360efd385d1a7d0659beba03787ea3d063ef9b PATCH https://github.com/python/cpython/commit/1be80bec7960f5ccd059e75f3dfbd45fca302947 PATCH https://github.com/python/cpython/commit/9060b4abbe475591b6230b23c2afefeff26fcca5 PATCH https://github.com/python/cpython/commit/e95e783dff443b68e8179fdb57737025bf02ba76 PATCH https://github.com/python/cpython/commit/fd17ee026fa9b67f6288cbafe374a3e479fe03a5 PATCH https://github.com/python/cpython/pull/141128 ADVISORY https://mail.python.org/archives/list/security-announce@python.org/thread/KRI7GC6S27YV5NJ4FPDALS2WI5ENAFJ6/ ADVISORY https://vuldb.com/vuln/342229 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0693/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0767/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20665/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20710/

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