Vulnerability in fastfeedparser (CVE-2026-39376)
Summary
Vulnerability in fastfeedparser (CVE-2026-39376). Risk of unauthorized operations or information disclosure. Exploitable via ValueError. Mitigation: upgrade to 0.5.10 or later.
Original description
The description as published by the source.
Summary
When parse() fetches a URL that returns an HTML page containing a `` tag, it recursively calls itself with the redirect URL — with no depth limit, no visited-URL deduplication, and no redirect count cap. An attacker-controlled server that returns an infinite chain of HTML meta-refresh responses causes unbounded recursion, exhausting the Python call stack and crashing the process. This vulnerability can also be chained with the companion SSRF issue to reach internal network targets after bypassing the initial URL check.
Details
parse() catches ValueError on XML parse failure, extracts a meta-refresh URL from the HTML response via _extract_meta_refresh_url(), and tail-calls itself with that URL. The recursive call is unconditional — there is no maximum redirect depth, no set of already-visited URLs, and no guard against self-referential or looping redirects.
fastfeedparser/main.py — parse() (recursive sink):
def parse(source: str | bytes, ...) -> FastFeedParserDict:
is_url = isinstance(source, str) and source.startswith(("http://", "https://"))
if is_url:
content = _fetch_url_content(source)
try:
return _parse_content(content, ...)
except ValueError as e:
...
redirect_url = _extract_meta_refresh_url(content, source)
if redirect_url is None:
raise
return parse(redirect_url, ...) # ← unconditional recursion, no depth limit
_extract_meta_refresh_url() us…
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
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-2026-39376 has been found in fastfeedparser.
Attackers can target a specific entry point like ValueError over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade fastfeedparser to 0.5.10 or later.
If unsure, ask your IT team or search "fastfeedparser CVE-2026-39376" on the vendor's site.
CVE-2026-39376 (fastfeedparser) — CWE-674 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: ValueError / _fetch_url_content / RecursionError
Patched: 0.5.10 — 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-674) exists in fastfeedparser. Attackers reach the vulnerable code path via ValueError without authentication.
Check the vendor advisory for the affected versions of fastfeedparser. Attack surface: ValueError / _fetch_url_content / RecursionError.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 0.5.10.
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 'fastfeedparser' . 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 'fastfeedparser' . | 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
fastfeedparser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 fastfeedparser to 0.5.10ステージング環境で 0.5.10 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
References
- advisory nvd.nist.gov
- exploit github.com
- package github.com
- web github.com
- web github.com