VulnerabilityPublished 29 Sep 2026

CVE-2026-102601: thephpleague flysystem · Improper Neutralization of Escape, Meta, or Control Sequences

Affects thephpleague flysystemSource CVE Database V5

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Not known to be exploited · CVSS 3.5 Low : upgrade to 3.35.3 when convenient.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score

3.5Low

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.35.3

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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 29 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 13 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

Upgrade flysystem and thephpleague/flysystem to 3.35.3.

Affected software

Product	Affected	Fixed in
thephpleagueflysystem	Affected <3.35.3	Fixed in 3.35.3
Packagistthephpleague/flysystem`pkg:composer/thephpleague/flysystem`Other threats	Affected <3.35.3	Fixed in 3.35.3

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

AI-suggested

A fixed version 3.35.3 of thephpleague flysystem is available that corrects the path normalization logic to properly handle malformed UTF-8 sequences and prevent bypass of corrupted path detection. Users should upgrade to version 3.35.3 or later to remediate this issue. No additional mitigation steps are indicated by the vendor advisory.

Description

CVE-2026-102601 affects thephpleague flysystem, an open source PHP file storage library. Prior to version 3.35.3, the default WhitespacePathNormalizer improperly handles paths containing malformed UTF-8 sequences. This allows certain control characters and raw ANSI escape sequences to bypass path normalization checks, potentially resulting in hidden or spoofed terminal file listings when administrators view directory contents. The issue is fixed in version 3.35.3.

Impact

This vulnerability allows an attacker to create file names containing control characters or raw ANSI escape sequences that bypass path normalization. When administrators list directory contents, these sequences can cause hidden or spoofed file listings in terminal displays. The impact is limited to information integrity and display spoofing, with no direct confidentiality or availability impact reported. The CVSS score is 3.5 (medium severity), indicating low impact on confidentiality and availability but some impact on integrity.

Summary

The vulnerability in thephpleague flysystem before version 3.35.3 arises from the default WhitespacePathNormalizer using preg_match with the 'u' modifier and treating false and 0 as falsy. When a path contains malformed UTF-8, PCRE returns false, causing the normalization function to bypass detection of corrupted paths. Consequently, Filesystem::write() can store file names with control characters, and Filesystem::listContents() can return raw ANSI escape sequences. This can lead to hidden or spoofed file listings in terminal outputs. The issue is addressed by fixing the normalization logic in version 3.35.3.

CWE-150Improper Neutralization of Escape, Meta, or Control Sequences (opens in a new tab)
Variant weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.
Developers should anticipate that escape, meta and control characters/sequences will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
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.
Implementation · Output Encoding
While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
V5.2.2 (opens in a new tab)
Attack patterns
Email Injection (opens in a new tab)
Using Meta-characters in E-mail Headers to Inject Malicious Payloads (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
Log Injection-Tampering-Forging (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 17 Oct 2026, 22:46 UTC

WeaknessesCWE-150

Technical details

References

Community reviews

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