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NVD / CVE Program· CNA GitHub_M

CVE-2023-25581: Deserialization of untrusted data in InternalAttributeHandler in pac4j

Noroxi assessment

Priority: Monitor (action score 37/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 80% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: org.pac4j:pac4j-core (Maven) 4.0.0.

Low priority for now. Upgrade to org.pac4j:pac4j-core (Maven) 4.0.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

pac4j is a security framework for Java. `pac4j-core` prior to version 4.0.0 is affected by a Java deserialization vulnerability. The vulnerability affects systems that store externally controlled values in attributes of the `UserProfile` class from pac4j-core. It can be exploited by providing an attribute that contains a serialized Java object with a special prefix `{#sb64}` and Base64 encoding. This issue may lead to Remote Code Execution (RCE) in the worst case. Although a `RestrictedObjectInputStream` is in place, that puts some restriction on what classes can be deserialized, it still allows a broad range of java packages and potentially exploitable with different gadget chains. pac4j versions 4.0.0 and greater are not affected by this issue. Users are advised to upgrade. There are no known workarounds for this vulnerability.

CriticalCVSS 9.2 · v4.0—Proof of concept Fix available
Published
Oct 10, 2024
Updated
Jun 17, 2026
EPSS
1.9% · 80th percentile

Report tools

JSON

Action score

37

Monitor

Low priority for now.

CVSS
36 / 40 · 9.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.9%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
9.2
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-25581

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
pac4jpac4j

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • pac4j pac4j

    • < 4.0.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Mavenorg.pac4j:pac4j-corebefore 4.0.04.0.0

Same product

pac4j: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-82463pac4j-core before 6.5.6 Authorization Bypass via Reversed Profile Type Check
    34Monitor
  • CVE-2026-82461pac4j-oidc before 6.5.6 Privilege Escalation via Unverified Keycloak Access Token
    34Monitor
  • CVE-2026-40459LDAP Injection in PAC4J
    34Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2019-10755Sep 23, 2019 · The SAML identifier generated within SAML2Utils.java was found to make use of the apache commons-lang3 RandomStringUtils class which makes t
    19Monitor
  • ← EarlierCVE-2021-44878Jan 6, 2022 · If an OpenID Connect provider supports the "none" algorithm (i.e., tokens with no signature), pac4j v5.3.0 (and prior) does not refuse it wi
    30Monitor
  • Later →CVE-2026-40458Apr 17, 2026 · Cross-Site Request Forgery in PAC4J
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Maven:org.pac4j:pac4j-core4.0.0Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:02024-10-15

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+4 d
  3. TodayNov 2, 2026+753 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-502 · Deserialization of Untrusted Data

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

Data received over the network is deserialized into the language’s native object format without verifying its source. Code paths inside the object can be triggered during deserialization.

The bug in code

The whole CWE-502 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

python
payload = sock.recv(65536)job = pickle.loads(payload)

Fixed

python
payload = sock.recv(65536)if not hmac.compare_digest(sign(payload), header_sig):    raise PermissionError("invalid signature")job = JobSchema.validate(json.loads(payload))

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records