Security readout for executives and security teams
Plain-English summary
CVE-2021-29157 affects Dovecot before 2.3.15. A local attacker could abuse path traversal during OAuth2 local JWT validation to make Dovecot use a signing key from an attacker-controlled filesystem location, potentially compromising authentication trust.
Executive priority
Treat as high priority for mail infrastructure using the affected OAuth2 configuration. It is not evidenced as actively exploited, but successful abuse could undermine authentication integrity on sensitive messaging systems.
Technical view
The issue is a ../ path traversal in Dovecot OAuth2 local JWT validation when using the posix fs driver. With local filesystem access and low privileges, an attacker may influence HS256 validation key selection. CVSS 3.1 is 7.5 with high confidentiality and integrity impact.
Likely exposure
Exposure is most likely on Dovecot installations before 2.3.15 that use OAuth2 local JWT validation with the posix fs driver. Systems without that configuration, or without attacker local filesystem access, appear less exposed based on the source bundle.
Exploitation context
The bundle does not cite active exploitation, and KEV is false. Exploitation is local, requires privileges and high attack complexity, and depends on a specific OAuth2 JWT validation configuration.
Researcher notes
Key constraints are local attack vector, required low privileges, high complexity, and configuration dependency. The source bundle lists no CWE and incomplete affected-product metadata, so validation should focus on Dovecot version and OAuth2 JWT local validation paths.
Mitigation direction
- Upgrade Dovecot to 2.3.15 or a vendor-fixed package.
- Apply Fedora or Gentoo package updates where those distributions are used.
- Review Dovecot OAuth2 local JWT validation configuration for posix fs driver usage.
- Restrict local filesystem write access around validation key paths.
- Check Dovecot vendor guidance for any deployment-specific hardening.
Validation and detection
- Inventory Dovecot versions and flag anything before 2.3.15.
- Identify systems using OAuth2 local JWT validation.
- Confirm whether the posix fs driver is configured for local JWT validation.
- Verify installed package versions against Dovecot, Fedora, or Gentoo advisories.
- Review authentication logs for unusual OAuth2 validation failures or configuration changes.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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File access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-29157 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AC:H/AV:L/A:N/C:H/I:H/PR:L/S:C/UI:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AC:H/AV:L/A:N/C:H/I:H/PR:L/S:C/UI:N1.15.8Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AC:H/AV:L/A:N/C:H/I:H/PR:L/S:C/UI:N
Source materials
- CVE List V5 sourceCVE List V5
- https://dovecot.org/securityCVE reference · x_refsource_MISC
- https://www.openwall.com/lists/oss-security/2021/06/28/1CVE reference · x_refsource_CONFIRM
- FEDORA-2021-208340a217CVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-891c1ab1acCVE reference · vendor-advisory, x_refsource_FEDORA
- GLSA-202107-41CVE reference · vendor-advisory, x_refsource_GENTOO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.