VulnerabilityPublished 6 Aug 2026

CVE-2026-61632: facelessuser pymdown-extensions · Path Traversal

Affects facelessuser pymdown-extensionsSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 11.0 when convenient.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 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 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 11.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
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: 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: None: There is no loss of integrity within 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 6 Aug 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 5 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 facelessuser pymdown-extensions to 11.0.

Affected software

Product	Affected	Fixed in
facelessuserpymdown-extensions	Affected <11.0	Fixed in 11.0
PyPIpymdown-extensions`pkg:pypi/pymdown-extensions`Other threats	Affected <=10.21.3	Fixed in–

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

AI-suggested

Upgrade PyMdown Extensions to version 11.0 or later, where this path traversal vulnerability in the b64 extension has been fixed. Until then, avoid enabling the b64 extension on untrusted Markdown input or restrict input sources to trusted users only. Patch status is not explicitly stated in the vendor advisory, but the fix is included starting with version 11.0.

Description

### Summary The `b64` extension inlines images referenced by `<img src="...">` as base64 data URIs. When resolving the `src` path it joins it onto the configured `base_path` with `os.path.normpath` and opens the result directly, with no check that the resolved path stays inside `base_path`. A `src` containing `../` sequences, or an absolute path, therefore reads a file outside `base_path` as long as that file has an allowed image extension (`.png`, `.jpg`, `.jpeg`, `.gif`, `.svg`). The base64 of that file is then embedded in the rendered output, disclosing its contents. This is a separate code path from the `snippets` traversal issues (GHSA-jh85-wwv9-24hv, GHSA-62q4-447f-wv8h). It lives in `pymdownx/b64.py` and has no path restriction of any kind. Confirmed on `10.21.3` installed from PyPI. ### Details In `pymdownx/b64.py`, function `repl_path` (around lines 68 to 90 on `main`): ```python if is_absolute: file_name = os.path.normpath(path) # absolute src: base_path ignored entirely else: file_name = os.path.normpath(os.path.join(base_path, path)) # relative src: '../' escapes base_path if os.path.exists(file_name): ext = os.path.splitext(file_name)[1].lower() for b64_ext in file_types: if ext in b64_ext: with open(file_name, "rb") as f: # opened with no containment check ... ``` There is no `startswith(base_path)`, no `os.path.realpath` comparison, and no rejection of `..`. Both branches are reachable from an attacker-controlled `src`. ### PoC Reproduced against an unmodified `pymdown-extensions==10.21.3` from PyPI. The script creates a `base_path` directory and a PNG one level above it, then renders Markdown whose image `src` points outside `base_path`, and confirms the outside file's bytes appear base64-encoded in the output. ```python import base64, os, shutil, tempfile, markdown root = tempfile.mkdtemp() base_path = os.path.join(root, "docs"); os.makedirs(base_path) outside = os.path.join(root, "secret"); os.makedirs(outside) png = base64.b64decode( "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNk" "+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==" ) with open(os.path.join(outside, "secret.png"), "wb") as f: f.write(png) md = markdown.Markdown( extensions=["pymdownx.b64"], extension_configs={"pymdownx.b64": {"base_path": base_path}}, ) html = md.convert('<img src="../secret/secret.png">') assert base64.b64encode(png).decode() in html, "not leaked" print("LEAKED:", html) ``` Output: ``` LEAKED: <p><img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQ..."></p> ``` The base64 of a file outside `base_path` is present in the output. The absolute-path branch behaves the same way: an absolute `src` bypasses `base_path` entirely via `os.path.normpath(path)`. Both were confirmed leaking. ### Impact An application that renders untrusted Markdown with `pymdownx.b64` enabled exposes the contents of image-extension files on the server, or any path the process can read, to whoever controls the Markdown and whoever views the output. The reach is bounded by the image-extension check, so it is a targeted file read rather than full arbitrary read, but it still discloses file contents that were never meant to be exposed. ### Suggested fix Resolve the real path and require it to stay within `base_path` before opening: ```python file_name = os.path.realpath(os.path.join(base_path, path)) base_real = os.path.realpath(base_path) if file_name != base_real and not file_name.startswith(base_real + os.sep): return m.group(0) # leave the tag untouched; do not read outside base_path ``` The same containment check should apply to the absolute-path branch rather than trusting an absolute `src`. Using `realpath` instead of `abspath` also closes the related symlink-following gap in the snippets handler.

Impact

An attacker who can supply or control Markdown content rendered with pymdownx.b64 enabled can read arbitrary files with certain image extensions accessible to the process outside the intended base directory. This results in information disclosure limited to readable image-extension files. There is no impact on integrity or availability. The CVSS 3.1 base score is 5.3 (medium severity), reflecting network attack vector, no privileges required, no user interaction, and limited confidentiality impact.

Summary

The b64 extension of PyMdown Extensions (up to version 10.21.3) improperly limits pathname resolution when inlining images referenced by <img src="..."> tags. It joins the src attribute onto a configured base_path using os.path.normpath but does not verify that the resulting path remains within base_path. This allows path traversal via '../' sequences or absolute paths to read files outside the intended directory, provided the files have allowed image extensions (.png, .jpg, .jpeg, .gif, .svg). The contents of these files are base64-encoded into the rendered Markdown output, leading to disclosure of arbitrary file contents accessible by the process. This vulnerability is tracked as CVE-2026-61632 and is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory).

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).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Aug 2026, 16:06 UTC

WeaknessesCWE-22

Technical details

References

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