How severe is CVE-2020-17527?

CVE-2020-17527 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-17527?

CVE-2020-17527 affects the following packages: org.apache.tomcat:tomcat-coyote (Maven), org.apache.tomcat:tomcat-coyote (Maven), org.apache.tomcat:tomcat-coyote (Maven). Ecosystems affected: Maven.

How do I fix CVE-2020-17527?

Update org.apache.tomcat:tomcat-coyote to 10.0.0-M10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-17527 is resolved across your whole dependency graph.

How do I detect CVE-2020-17527 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat-coyote. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2020-17527 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2020-17527?

O3 pinpoints whether CVE-2020-17527 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2020-17527 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-17527 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is CVE-2020-17527?

CVE-2020-17527 is classified as Information Exposure (CWE-200). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-17527 published, and has it been updated?

CVE-2020-17527 was published on December 3, 2020 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2020-17527

HIGH

CVE-2020-17527 is a high-severity (CVSS 7.5) Information Exposure vulnerability in org.apache.tomcat:tomcat-coyote. O3 Security confirms whether CVE-2020-17527 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Exposure of Sensitive Information to an Unauthorized Actor in Apache Tomcat

Also known asBIT-tomcat-2020-17527GHSA-vvw4-rfwf-p6hx

Published

Dec 3, 2020

Updated

Jul 8, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Jul 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

3 pkgs affected

☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

While investigating bug 64830 it was discovered that Apache Tomcat 10.0.0-M1 to 10.0.0-M9, 9.0.0-M1 to 9.0.39 and 8.5.0 to 8.5.59 could re-use an HTTP request header value from the previous stream received on an HTTP/2 connection for the request associated with the subsequent stream. While this would most likely lead to an error and the closure of the HTTP/2 connection, it is possible that information could leak between requests.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.tomcat:tomcat-coyote`	≥ 10.0.0-M1&&< 10.0.0-M10	10.0.0-M10
☕Maven	`org.apache.tomcat:tomcat-coyote`	≥ 9.0.0-M1&&< 9.0.40	9.0.40
☕Maven	`org.apache.tomcat:tomcat-coyote`	≥ 8.5.0&&< 8.5.60	8.5.60

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat-coyote. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.apache.tomcat:tomcat-coyote to 10.0.0-M10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-17527 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2020-17527 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2020-17527. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2020-17527 in your dependencies?

O3 detects CVE-2020-17527 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works