Vikunja before 2.6.0 Denial of Service via Avatar Upload

published 2026-09-15 54 d ago modified 2026-10-19 20 d ago also GHSA-4vh2-39rq-rq8j , GO-2026-6717 , EUVD-2026-78647

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits: 0; none known

Vikunja before 2.6.0 fails to apply pixel decode limits to avatar and project-background upload endpoints, allowing authenticated users to upload crafted images that decode to excessive pixel counts. Attackers can upload small images with extreme aspect ratios that consume significant CPU and memory during processing, causing denial of service through repeated or concurrent uploads.

Patch / fix

fixed in 2 links 2

go code.vikunja.io/api 2.6.0
go-vikunja vikunja 2.6.0

github.com/go-vikunja/vikunja#3688 pull request
github.com/go-vikunja/vikunja/releases/tag/v2.6.0 release

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 48 d ago (2026-09-21)

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/go-vikunja/vikunja/security/advisories/GHSA-4vh2-39rq-rq8j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	7.1	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA	4.0	7.1	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem	package	affected	fixed in
go	code.vikunja.io/api	<2.6.0 all versions	2.6.0

Affected products

go-vikunja vikunja

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

References

github.com /go-vikunja/vikunja/pull/3688
web
github.com /go-vikunja/vikunja/security/advisories/GHSA-4vh2-39rq-rq8j
vendor-advisory, exploit, web, advisory
vulncheck.com /advisories/vikunja-before-2.6.0-denial-of-service-via-avatar-upload
third-party-advisory, web
nvd.nist.gov /vuln/detail/CVE-2026-91971
advisory
github.com /go-vikunja/vikunja
package
github.com /go-vikunja/vikunja/releases/tag/v2.6.0
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary