An attacker that holds an OAuth2 token granting only part of the required scopes can authenticate, because when more than one scope is requi
An attacker that holds an OAuth2 token granting only part of the required scopes can authenticate, because when more than one scope is required in the configuration, the remote token validation paths accept a token that carries only one of them, while the local token validation path correctly requires all of them. The configured authorization policy is not enforced, so a token that was granted only part of the required permissions is accepted where it should have been rejected. Use local token validation where tokens can be validated locally. Update to non-vulnerable version. No publicly available exploits are known.
- Published
- Aug 28, 2026
- Updated
- Sep 3, 2026
- EPSS
- 0.2% · 10th percentile
- CWE
- CWE-287
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Report tools
Action score
23
Monitor
Low priority for now.
- CVSS
- 23 / 40 · 5.9 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · OX
- 5.9
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (OX). Independent of NVD's CPE analysis and usually ahead of it.
Open-Xchange GmbH OX Dovecot CE
- 2.3.11.2 and later · before 2.4.5affected · semver
Open-Xchange GmbH OX Dovecot Pro
- 2.3.11.2 and later · before 2.3.22.2affected · semver
- 3.0.0 and later · before 3.0.7affected · semver
- 3.1.0 and later · before 3.1.6affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.23 | dovecot | before 2.4.5-r0 | 2.4.5-r0 |
| Debian:12 | dovecot | all versions | — |
| Debian:13 | dovecot | before 1:2.4.1+dfsg1-6+deb13u7 | 1:2.4.1+dfsg1-6+deb13u7 |
| Debian:14 | dovecot | before 1:2.4.5+dfsg1-1 | 1:2.4.5+dfsg1-1 |
| openSUSE:Leap 16.0 | dovecot24 | before 2.4.4-160000.2.1 | 2.4.4-160000.2.1 |
| openSUSE:Tumbleweed | dovecot24 | before 2.4.5-1.1 | 2.4.5-1.1 |
| SUSE:Linux Enterprise Server 16.0 | dovecot24 | before 2.4.4-160000.2.1 | 2.4.4-160000.2.1 |
Same product
open-xchange gmbh: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-42007An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing 36Monitor
- CVE-2026-42391An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CP30Monitor
- CVE-2026-33605An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating.30Monitor
- CVE-2026-27852An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters30Monitor
- CVE-2024-23185Very large headers can cause resource exhaustion when parsing message.30Monitor
- CVE-2026-73208An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a s29Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Open-Xchange GmbH OX Dovecot CE | 2.4.5 | Vendor (CNA) |
| Open-Xchange GmbH OX Dovecot Pro | 2.3.22.2 | Vendor (CNA) |
| Open-Xchange GmbH OX Dovecot Pro | 3.0.7 | Vendor (CNA) |
| Open-Xchange GmbH OX Dovecot Pro | 3.1.6 | Vendor (CNA) |
| alpine:dovecot | 2.4.5-r0 · Alpine:v3.23 | Package registry (OSV) |
| debian:dovecot | 1:2.4.1+dfsg1-6+deb13u7 · Debian:13 | Package registry (OSV) |
| opensuse:dovecot24 | 2.4.5-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| suse:dovecot24 | 2.4.4-160000.2.1 · SUSE:Linux Enterprise Server 16.0 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
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.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
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 researchersFinders, 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.
- CVE-2026-732080 days apartAn attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a s29Monitor
- CVE-2026-420080 days apartForwarding information received from a host listed as a trusted proxy is not kept separate from Dovecot's own authentication fields, so a va17Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
- CVE-2026-420070 days apartAn attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing 36Monitor
- CVE-2026-400130 days apartAn attacker that has valid credentials can submit a Sieve script containing an extreme numeric literal, which causes an out-of-bounds write 17Monitor
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.
- A low-privileged account is enough.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- low · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-287 · Improper AuthenticationCVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
nvd-secondary
Root cause
Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.
The bug in code
The whole CWE-287 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
app.use("/admin", requireSession, adminRouter);
// Route added later skips the middlewareapp.post("/admin-api/config", updateConfig);Fixed
const admin = express.Router();admin.use(requireSession, requireRole("admin"));
admin.post("/config", updateConfig);app.use("/admin", admin);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Authentication AbuseCAPEC-114Medium
- Authentication BypassCAPEC-115Medium
- Identity SpoofingCAPEC-151likelihood: Medium · Medium
- Fake the Source of DataCAPEC-194Medium
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Utilizing REST's Trust in the System Resource to Obtain Sensitive DataCAPEC-57likelihood: Medium · Very High
- Session HijackingCAPEC-593likelihood: High · Very High
- Token ImpersonationCAPEC-633Medium
ATT&CK techniques
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
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References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.