VulnerabilityPublished 30 Sep 2026Updated 5 Oct 2026

CVE-2026-103001: jpadilla pyjwt · Modification of Assumed-Immutable Data (MAID)

Affects jpadilla pyjwtSource CVE Database V5

Compare

Not known to be exploited · CVSS 6.5 Medium.

Data as of 14 Nov 2026, 20:43 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: High
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 30 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 14 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity 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
jpadillapyjwt	Affected >=2.11.0 <=2.13.0	Fixed in–
PyPIpyjwt`pkg:pypi/pyjwt`Other threats	Affected >=2.11.0 <=2.13.0	Fixed in–

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

AI-suggested

The suggested fix is to modify the _merge_options() method to create a shallow copy of the options dictionary before mutating it, preventing caller-side mutation. Until an official fix is released, users should avoid reusing the same mutable options dictionary across multiple decode() or decode_complete() calls with different verification settings. Constructing a fresh options dictionary per call prevents this vulnerability from being triggered. Monitor the PyJWT repository and vendor advisories for an official patch or update.

Description

PyJWT versions 2.11.0 through 2.13.0 contain a vulnerability where the decode() and decode_complete() functions mutate a caller-supplied options dictionary when signature verification is disabled. This mutation can cause subsequent calls that enable signature verification to inherit disabled claim checks such as expiration, audience, issuer, and subject verification, allowing acceptance of tokens with invalid claims without raising exceptions. This is a claims verification bypass, not a signature verification bypass. The issue is a regression introduced in March 2025 by a refactor that removed a shallow copy of the options dictionary. The vulnerability requires the application to reuse the same mutable options dictionary across decode calls with different verification intents.

Impact

When exploited, this vulnerability allows an attacker to bypass claim verification checks such as expiration, audience, issuer, subject, and token identifiers if the application reuses the same mutable options dictionary across decode calls with different verification settings. This can lead to acceptance of expired or otherwise invalid tokens as valid, resulting in authentication and claims verification bypass. Signature verification itself remains intact, so the flaw does not allow signature forgery. The vulnerability requires a specific application pattern (reuse of mutable options dict) to be exploitable.

Summary

The vulnerability (CVE-2026-103001) in jpadilla's PyJWT library arises from the _merge_options() method mutating the caller-supplied options dictionary in place when verify_signature is false. This mutation adds keys disabling claim verifications (e.g., verify_exp, verify_nbf) directly onto the caller's dictionary. If the same options dictionary is reused in a subsequent decode call with verify_signature set to true, the leftover disabled claim checks cause the library to accept tokens with expired or otherwise invalid claims without exception. This flaw is a regression of a previously fixed issue due to removal of a shallow copy of the options dictionary in a 2025 refactor (PR #1045). It affects all PyJWT releases from 2.11.0 through 2.13.0. The recommended fix is to restore a shallow copy of the options dictionary inside _merge_options() to avoid mutating caller data.

CWE-471Modification of Assumed-Immutable Data (MAID) (opens in a new tab)
Base weaknessOWASP Top 10 A03:2021: Injection (opens in a new tab)
The product does not properly protect an assumed-immutable element from being modified by an attacker.
Architecture and Design · Operation · Implementation
When the data is stored or transmitted through untrusted sources that could modify the data, implement integrity checks to detect unauthorized modification, or store/transmit the data in a trusted location that is free from external influence.
Attack patterns
Application API Message Manipulation via Man-in-the-Middle (opens in a new tab)
Transaction or Event Tampering via Application API Manipulation (opens in a new tab)
Application API Navigation Remapping (opens in a new tab)
Navigation Remapping To Propagate Malicious Content (opens in a new tab)
Application API Button Hijacking (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 17 Oct 2026, 22:44 UTC

WeaknessesCWE-471

Technical details

References

Community reviews

Related threats