Vulnerability in thumbor (CVE-2026-53504)
Summary
Vulnerability in thumbor (CVE-2026-53504). Risk of unauthorized operations or information disclosure. Exploitable via convolution. Mitigation: upgrade to 7.8.0 or later.
Original description
The description as published by the source.
Summary
The regular expression used to parse the convolution filter exhibits exponential-time backtracking for certain inputs, enabling a Regular Expression Denial of Service (ReDoS).
Details
The RegExp for convolution is defined as convolution\((?:\s*((?:[-]?[\d]+\.?[\d]*[;])*(?:[-]?[\d]+\.?[\d]*))\s*)(?:,\s*([\d]+)\s*)(?:,\s*([Tt]rue|[Ff]alse|1|0)\s*)?\). Within this expression a dangerous subpattern effectively behaves like (\d+)*,\d+.
PoC
A filter string containing many repeated values will exhaust re.match:
convolution(-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11)- http://localhost:8888/unsafe/0x0/smart/filters:convolution(-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11;-11)/x.png
The evaluation occurs on https://github.com/thumbor/thumbor/blob/master/thumbor/filters/__init__.py#L189.
Impact
A specially crafted URL will lead to denial of service, as new images won't be processed until re.match returns.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-53504 has been found in thumbor.
Attackers can target a specific entry point like convolution over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade thumbor to 7.8.0 or later.
If unsure, ask your IT team or search "thumbor CVE-2026-53504" on the vendor's site.
CVE-2026-53504 (thumbor) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: convolution / re.match
Patched: 7.8.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in thumbor. Attackers reach the vulnerable code path via convolution without authentication.
Check the vendor advisory for the affected versions of thumbor. Attack surface: convolution / re.match.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 7.8.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'thumbor' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'thumbor' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
thumborを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade thumbor to 7.8.0ステージング環境で 7.8.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-53504 thumbor Fixed in: 7.8.0-1
- Ubuntu UBUNTU-CVE-2026-53504 thumbor
References
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- package pypi.org
- web github.com
- web github.com
- web github.com