CVE-2026-107566
Missing Authorization in hMailServer
02 Description
Missing Authorization in hMailServer
03 Exploitation and scoring
- Exploitation
- Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
- SSVC decision
- ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
- AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
- Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
- EPSS probability
- 0.18% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 7.2% of scored records. A rank, not a probability.
- NVD base score
- 6.5 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- NVD analysis status
- Deferred. NVD last modified this record on 2026-10-20.
- Red Hat severity
- No Red Hat rating. Red Hat rates the CVEs that affect its products.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2026-10-19 15:34Z9 DAYS AGO
- Last updated
- 2026-10-20 19:25Z8 DAYS AGO
- Reserved
- 2026-10-08
- Assigning CNA
- GitLab
- Record state
- PUBLISHED
- Severity
- Medium (CVSS 6.5)
- CNA CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- Weaknesses
- CWE-862Missing AuthorizationClass
- Data version
- 5.2
- Document digest
- fe82152430f999f28b7c5a350dee9c73927fa19a5cef49d2751ef4b972199ac5
05 Affected products
06 References
07 Remediation
Upgrade to hMailServer 6.3.7, which refuses a Sieve script that adds or deletes From, Sender, Resent-From, Resent-Sender or DKIM-Signature when the script is stored, and does not make such an edit at delivery for a script stored earlier (logged), while leaving Reply-To and other fields editable; and which lets only a server rule's Set header value action, which only the server administrator saves, set those five fields, refusing an account's or a domain's rule that sets one when it is saved and not setting it at delivery for one stored before (logged). Until then, where accounts need not set Sieve scripts, close the script surfaces: keep ManageSieve off (ManageSieveServerPort=0, the default) or bound to the loopback, and turn the REST API off where the webmail's filter editor is not wanted (RestApiPort=0, the default); and review active Sieve scripts for an addheader or deleteheader of From, Sender, Resent-From, Resent-Sender or DKIM-Signature followed by a redirect, and account and domain rules for a Set header value of one of those fields. There is no per-extension setting that turns editheader off while Sieve is in use.