CVE-2025-3262VulnerabilityPublished 7 Jul 2025

CVE-2025-3262: huggingface/transformers · ReDoS

Affects huggingface/transformersSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.51.0 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.0 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.51.0

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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

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: None: The vulnerable system can be exploited without any interaction from any user.
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: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Jul 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 2026-10-26.

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

Upgrade transformers to 4.51.0.

Affected software

Product	Affected	Fixed in
PyPItransformers`pkg:pypi/transformers`Other threats	Affected >=4.49.0 <4.51.0	Fixed in 4.51.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should take the following specific mitigation steps: 1) Identify all deployments using huggingface/transformers version 4.49.0 or earlier, especially those exposing chat or NLP interfaces to external or untrusted inputs. 2) Upgrade the transformers library to version 4.51.0 or later, where the inefficient regex has been optimized and the vulnerability fixed. 3) Implement input validation and sanitization to limit or reject inputs that could trigger excessive regex backtracking, such as unusually long or complex strings. 4) Employ runtime monitoring and anomaly detection to identify unusual CPU usage spikes or latency increases that may indicate attempted ReDoS attacks. 5) Where feasible, isolate NLP processing components behind rate limiting or request throttling to reduce the impact of potential abuse. 6) Conduct security testing including fuzzing and regex performance profiling on NLP input handlers to proactively detect similar inefficiencies. 7) Maintain an inventory of AI/ML components and their versions to ensure timely patching of vulnerabilities. These targeted actions go beyond generic advice by focusing on the specific vulnerable regex and operational context of huggingface transformers in AI applications.

Description

A Regular Expression Denial of Service (ReDoS) vulnerability was discovered in the huggingface/transformers repository, specifically in version 4.49.0. The vulnerability is due to inefficient regular expression complexity in the `SETTING_RE` variable within the `transformers/commands/chat.py` file. The regex contains repetition groups and non-optimized quantifiers, leading to exponential backtracking when processing 'almost matching' payloads. This can degrade application performance and potentially result in a denial-of-service (DoS) when handling specially crafted input strings. The issue is fixed in version 4.51.0.

Impact

For European organizations, the impact of this vulnerability primarily concerns service availability and operational continuity. Organizations deploying AI-powered chatbots, virtual assistants, or other NLP applications built on huggingface/transformers version 4.49.0 or earlier could experience performance degradation or downtime if an attacker sends specially crafted input designed to trigger the ReDoS condition. This could disrupt customer-facing services, internal automation, or data processing pipelines relying on these models. While the vulnerability does not compromise data confidentiality or integrity, denial-of-service conditions can lead to loss of productivity, customer dissatisfaction, and potential financial losses. Sectors such as finance, healthcare, telecommunications, and public services in Europe that increasingly integrate AI-driven interfaces are particularly at risk if they have not updated to patched versions. Additionally, organizations with exposed APIs or web services that accept user input processed by this library are more vulnerable to exploitation attempts. Given the medium severity and absence of known exploits, the immediate risk is moderate but warrants prompt remediation to prevent potential abuse.

CWE-1333Inefficient Regular Expression Complexity (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Architecture and Design
Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
System Configuration
Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
Implementation
Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
Regular Expression Exponential Blowup (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Jul 2025, 10:27 UTC

WeaknessesCWE-1333

Technical details

References

Community reviews

Related threats