VDB-403212 · CVE-2026-90679 · EUVD-2026-76944

Forgejo up to 16.0.4 ActivityPub reqsignature.go signature verification

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.3	$0-$5k	2.27

Summaryinfo

A vulnerability described as problematic has been identified in Forgejo up to 16.0.4. The impacted element is an unknown function of the file routers/api/v1/activitypub/reqsignature.go of the component ActivityPub. The manipulation results in signature verification. This vulnerability is reported as CVE-2026-90679. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Forgejo up to 16.0.4. Affected is an unknown code block of the file routers/api/v1/activitypub/reqsignature.go of the component ActivityPub. The manipulation with an unknown input leads to a signature verification vulnerability. CWE is classifying the issue as CWE-347. The product does not verify, or incorrectly verifies, the cryptographic signature for data. This is going to have an impact on integrity. CVE summarizes:

Forgejo 13.0.0 through 16.0.4, when "[federation] ENABLED = true" is set, has a spoofing issue that affects identity integrity but does not allow account takeover or content modification. It does not verify that the HTTP Signature on an incoming ActivityPub activity was produced by the key belonging to the actor named in the activity body. The signature verification in routers/api/v1/activitypub/reqsignature.go validates the request signature, but the inbox activity handlers subsequently read the acting identity from the attacker-controlled JSON body without binding it to the verified signing key. Additionally, the signed Digest header is not recomputed against the received request body. A remote attacker who hosts a single valid ActivityPub actor and keypair can therefore submit signature-valid activities attributed to any actor identity they name.

The advisory is shared for download at codeberg.org. This vulnerability is traded as CVE-2026-90679 since 09/13/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are known technical details, but no exploit is available.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-76944). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

Forgejo

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.3
CNA Vector (MITRE): 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Signature verification
CWE: CWE-347 / CWE-345
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

09/13/2026 Advisory disclosed
09/13/2026 +0 days CVE reserved
09/13/2026 +0 days VulDB entry created
09/13/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: codeberg.org
Status: Not defined

CVE: CVE-2026-90679 (🔒)
GCVE (CVE): GCVE-0-2026-90679
GCVE (VulDB): GCVE-100-403212
EUVD: 🔒

Entryinfo

Created: 09/13/2026 06:22
Updated: 09/13/2026 07:43
Changes: 09/13/2026 06:22 (61), 09/13/2026 07:43 (1)
Complete: 🔍
Cache ID: 216::103