Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST reque
Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST request. This affects Varnish Enterprise 6.0.x before 6.0.8r3, and Varnish Cache 5.x and 6.x before 6.5.2, 6.6.x before 6.6.1, and 6.0 LTS before 6.0.8.
- Published
- Jul 14, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.6% · 75th percentile
- CWE
- CWE-444
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Report tools
Action score
26
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.6%
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| varnish-cache | varnish cache | cpe:2.3:a:varnish-cache:varnish_cache |
| varnish-software | varnish cache | cpe:2.3:a:varnish-software:varnish_cache |
| varnish cache project | varnish cache | cpe:2.3:a:varnish_cache_project:varnish_cache |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux10.0
- debian debian linux11.0
- fedoraproject fedora33
- fedoraproject fedora34
- varnish cache project varnish cache6.1.0 and later · up to 6.6.0 inclusive
- varnish cache project varnish cache5.0.0 and later · up to 5.2.1 inclusive
- varnish-cache varnish cache6.0.0 and later · before 6.0.8
- varnish-cache varnish cache6.0.8
- varnish-software varnish cache6.0.0 and later · up to 6.0.7 inclusive
- varnish-software varnish cache6.0.0 and later · up to 6.0.5 inclusive
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.11 | varnish | before 6.5.2-r0 | 6.5.2-r0 |
| Alpine:v3.14 | varnish | before 6.6.1-r0 | 6.6.1-r0 |
| Debian:10 | varnish | before 6.1.1-1+deb10u3 | 6.1.1-1+deb10u3 |
| Debian:11 | varnish | before 6.5.1-1+deb11u2 | 6.5.1-1+deb11u2 |
| Debian:12 | varnish | before 6.5.2-1 | 6.5.2-1 |
| Red Hat:enterprise_linux:8::appstream | varnish | before 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 |
| Red Hat:enterprise_linux:8::appstream | varnish-devel | before 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 |
| Red Hat:enterprise_linux:8::appstream | varnish-docs | before 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 |
| Red Hat:enterprise_linux:8::appstream | varnish-modules | before 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc | 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc |
| Red Hat:enterprise_linux:8::appstream | varnish-modules-debuginfo | before 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc | 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc |
| Red Hat:enterprise_linux:8::appstream | varnish-modules-debugsource | before 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc | 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc |
| Red Hat:rhel_eus:8.1::appstream | varnish | before 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 |
| Red Hat:rhel_eus:8.1::appstream | varnish-devel | before 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 |
| Red Hat:rhel_eus:8.1::appstream | varnish-docs | before 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 |
| Red Hat:rhel_eus:8.1::appstream | varnish-modules | before 0:0.15.0-4.module+el8+2481+4078e9d2 | 0:0.15.0-4.module+el8+2481+4078e9d2 |
| Red Hat:rhel_eus:8.1::appstream | varnish-modules-debuginfo | before 0:0.15.0-4.module+el8+2481+4078e9d2 | 0:0.15.0-4.module+el8+2481+4078e9d2 |
| Red Hat:rhel_eus:8.1::appstream | varnish-modules-debugsource | before 0:0.15.0-4.module+el8+2481+4078e9d2 | 0:0.15.0-4.module+el8+2481+4078e9d2 |
| Red Hat:rhel_eus:8.2::appstream | varnish | before 0:6.0.2-2.module+el8.2.0+11973+a748eca7 | 0:6.0.2-2.module+el8.2.0+11973+a748eca7 |
| Red Hat:rhel_eus:8.2::appstream | varnish-devel | before 0:6.0.2-2.module+el8.2.0+11973+a748eca7 | 0:6.0.2-2.module+el8.2.0+11973+a748eca7 |
| Red Hat:rhel_eus:8.2::appstream | varnish-docs | before 0:6.0.2-2.module+el8.2.0+11973+a748eca7 | 0:6.0.2-2.module+el8.2.0+11973+a748eca7 |
| Red Hat:rhel_software_collections:3::el7 | rh-varnish6-varnish | before 0:6.0.8-2.el7 | 0:6.0.8-2.el7 |
| Red Hat:rhel_software_collections:3::el7 | rh-varnish6-varnish-devel | before 0:6.0.8-2.el7 | 0:6.0.8-2.el7 |
| Red Hat:rhel_software_collections:3::el7 | rh-varnish6-varnish-docs | before 0:6.0.8-2.el7 | 0:6.0.8-2.el7 |
| Red Hat:rhel_software_collections:3::el7 | rh-varnish6-varnish-libs | before 0:6.0.8-2.el7 | 0:6.0.8-2.el7 |
+6
Same product
varnish-cache: all recordsOther highest-scoring records for the same primary product.
- CVE-2020-11653An issue was discovered in Varnish Cache before 6.0.6 LTS, 6.1.x and 6.2.x before 6.2.3, and 6.3.x before 6.3.2.31Monitor
- CVE-2019-20637An issue was discovered in Varnish Cache before 6.0.5 LTS, 6.1.x and 6.2.x before 6.2.2, and 6.3.x before 6.3.1.31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| alpine:varnish | 6.5.2-r0 · Alpine:v3.11 | Package registry (OSV) |
| debian:varnish | 6.5.2-1 · Debian:12 | Package registry (OSV) |
| opensuse:varnish | 7.1.0-bp153.2.3.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| red hat:rh-varnish6-varnish | 0:6.0.8-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-varnish6-varnish-devel | 0:6.0.8-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-varnish6-varnish-docs | 0:6.0.8-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-varnish6-varnish-libs | 0:6.0.8-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-varnish6-varnish-modules | 0:0.15.0-7.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-varnish6-varnish-modules-debuginfo | 0:0.15.0-7.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:varnish | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| red hat:varnish-devel | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| red hat:varnish-docs | 0:6.0.2-2.module+el8.1.0+11974+ea5ba4f1 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| red hat:varnish-modules | 0:0.15.0-4.module+el8+2481+4078e9d2 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| red hat:varnish-modules-debuginfo | 0:0.15.0-4.module+el8+2481+4078e9d2 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| red hat:varnish-modules-debugsource | 0:0.15.0-4.module+el8+2481+4078e9d2 · Red Hat:rhel_eus:8.1::appstream | Package registry (OSV) |
| rocky linux:varnish | 0:6.0.6-2.module+el8.3.0+179+20b582cc · Rocky Linux:8 | Package registry (OSV) |
| rocky linux:varnish-modules | 0:0.15.0-5.module+el8.3.0+179+20b582cc · Rocky Linux:8 | Package registry (OSV) |
| suse:varnish | 7.1.0-bp153.2.3.1 · SUSE:Package Hub 15 SP3 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-21-0603 · Aug 3, 2021(RedHat Güvenlik Güncellemesi Yayınladı)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- docs.varnish-software.com/security/VSV00007/
- github.com/varnishcache/varnish-cache/commit/82b0a629f60136e76112c6f2c6372cce77b683be
- github.com/varnishcache/varnish-cache/commit/9be22198e258d0e7a5c41f4291792214a29405cf
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THV2DQA2GS65HUCKK4KSD2XLN3AAQ2V5/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZHBNLDEOTGYRIEQZBWV7F6VPYS4O2AAK/
- varnish-cache.org/security/VSV00007.html
- www.debian.org/security/2022/dsa-5088
Vendor advisories and official records. Exploit/PoC links are deliberately left out.