Security Digest · Vulnerability record
CVE-2026-3490: PickleScan's pkgutil.resolve_name has a universal blocklist bypass
picklescan before 1.0.4 fails to block pkgutil.resolvename, allowing attackers to bypass the entire blocklist by resolving any dangerous function through indirect REDUCE calls.
CVSS 10.0 Critical EPSS 0.9% · p60
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.9%, percentile 60: FIRST’s model estimates a 0.9% chance of exploitation activity in the next 30 days, higher than 60% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
picklescan(PyPI) < 1.0.4, fixed in 1.0.4. Check your lockfile, including transitive dependencies.
What it is
picklescan before 1.0.4 fails to block pkgutil.resolvename, allowing attackers to bypass the entire blocklist by resolving any dangerous function through indirect REDUCE calls. Remote attackers can invoke any blocked function such as os.system, builtins.exec, or subprocess.call to achieve remote code execution.
From the GitHub advisory
Summary
pkgutil.resolvename() is a Python stdlib function that resolves any "module:attribute" string to the corresponding Python object at runtime. By using pkgutil.resolvename as the first REDUCE call in a pickle, an attacker can obtain a reference to ANY blocked function (e.g., os.system, builtins.exec, subprocess.call) without that function appearing in the pickle's opcodes. picklescan only sees pkgutil.resolvename (which is not blocked) and misses the actual dangerous function entirely.
This defeats picklescan's entire blocklist concept — every single entry in unsafeglobals can be bypassed.
Severity
Critical (CVSS 10.0) — Universal bypass of all blocklist entries. Any blocked function can be invoked.
Weakness type: CWE-183, CWE-693.
Product: picklescan (PyPI) · Assigned by: VulnCheck · Published: 2026-06-17
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | picklescan | < 1.0.4 | 1.0.4 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| picklescan | picklescan | < 1.0.4 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| VulnCheck | 4.0 | 10 Critical | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H |
| VulnCheck | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Attack requirements: none
- Privileges required: none (no login)
- User interaction: none
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.91% probability of exploitation activity in the next 30 days; percentile 60.
Timeline
- — GitHub-reviewed advisory GHSA-vvpj-8cmc-gx39 published (critical)
- — CVE record published by VulnCheck
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- GHSA Advisory GHSA-vvpj-8cmc-gx39 github.com
Vulnerability records
- GitHub Advisory GHSA-vvpj-8cmc-gx39 github.com
- CVE.org record CVE-2026-3490 cve.org
- NVD entry CVE-2026-3490 nvd.nist.gov