VulnerabilityPublished 5 Nov 2026

CVE-2026-123204: goposta posta · Server-Side Request Forgery (SSRF)

Affects goposta postaSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to v0.18.0 when convenient.

Data as of 5 Nov 2026, 20:17 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (VulnCheck)	CVSS 4.0	5.3
CNA (VulnCheck)	CVSS 3.1	4.3

Patch: Available – fixed in v0.18.0, 0.18.0

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade posta to v0.18.0; posta to 0.18.0.

Affected software

Product	Affected	Fixed in
gopostaposta	Affected <0.18.0	Fixed in v0.18.0
Goposta`pkg:golang/posta`Other threats	Affected <0.18.0	Fixed in 0.18.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade goposta posta to version 0.18.0 or later, where this SSRF vulnerability has been fixed. No other specific mitigations are indicated by the vendor advisory.

Description

CVE-2026-123204 is a server-side request forgery (SSRF) vulnerability in goposta posta versions before 0.18.0. Authenticated users with edit rights can exploit this flaw by creating webhooks with arbitrary URLs, causing the backend to send POST requests to internal network destinations. This allows attackers to probe internal hosts and ports, including loopback, private network, or cloud metadata addresses, by reading delivery status codes and error messages. The vulnerability has a medium severity with a CVSS score of 5.3. It was fixed in version 0.18.0.

Impact

Exploitation of this SSRF vulnerability enables authenticated users with edit rights to make the server send POST requests to internal network destinations. This can be used to probe internal hosts and ports, potentially revealing sensitive information such as delivery status codes and error strings. While it does not directly allow remote code execution or data exfiltration, it can facilitate further internal reconnaissance and attacks.

Summary

The vulnerability in goposta posta (CVE-2026-123204) allows authenticated users with edit permissions to perform SSRF attacks by configuring webhooks that cause the backend to send POST requests to arbitrary internal URLs. This can be used to access internal network resources such as loopback interfaces, private network addresses, or cloud metadata services. The flaw exists in all versions prior to 0.18.0 and was addressed by a fix in version 0.18.0. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges required beyond edit rights, no user interaction, and low scope impact.

References

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