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NVD / CVE Program· CNA GitHub_M

CVE-2021-32779: Incorrectly handling of URI '#fragment' element as part of the path element

Noroxi assessment

Priority: Monitor (action score 33/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.94% (FIRST EPSS); higher than 61.2% of all records.
  • 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.
  • Fixed version: servicemesh (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8; servicemesh-citadel (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8; servicemesh-galley (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8.

Low priority for now. Upgrade to servicemesh (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8; servicemesh-citadel (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8; servicemesh-galley (Red Hat:service_mesh:1.1::el8) 0:1.1.17-3.el8 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy incorrectly handled a URI '#fragment' element as part of the path element. Envoy is configured with an RBAC filter for authorization or similar mechanism with an explicit case of a final "/admin" path element, or is using a negative assertion with final path element of "/admin". The client sends request to "/app1/admin#foo". In Envoy prior to 1.18.0, or 1.18.0+ configured with path_normalization=false. Envoy treats fragment as a suffix of the query string when present, or as a suffix of the path when query string is absent, so it evaluates the final path element as "/admin#foo" and mismatches with the configured "/admin" path element. In Envoy 1.18.0+ configured with path_normalization=true. Envoy transforms this to /app1/admin%23foo and mismatches with the configured /admin prefix. The resulting URI is sent to the next server-agent with the offending "#foo" fragment which violates RFC3986 or with the nonsensical "%23foo" text appended. A specifically constructed request with URI containing '#fragment' element delivered by an untrusted client in the presence of path based request authorization resulting in escalation of Privileges when path based request authorization extensions. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes that removes fragment from URI path in incoming requests.

HighCVSS 8.3 · v3.1—No exploit Fix available
Published
Aug 24, 2021
Updated
Jun 16, 2026
EPSS
0.9% · 61th percentile

Report tools

JSON

Action score

33

Monitor

Low priority for now.

CVSS
33 / 40 · 8.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

CNA vs NVD score

NVD
8.3
CNA · GitHub_M
8.6
0.3 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
envoyproxyenvoy

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • envoyproxy envoy1.16.0 and later · before 1.16.5
  • envoyproxy envoy1.17.0 and later · before 1.17.4
  • envoyproxy envoy1.18.0 and later · before 1.18.4
  • envoyproxy envoy1.19.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • envoyproxy envoy

    • >= 1.19.0, < 1.19.1, >= 1.18.0, < 1.18.4, >= 1.17.0, < 1.17.4, >= 1.16.0, < 1.16.5affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Red Hat:service_mesh:1.1::el8servicemeshbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-citadelbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-galleybefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-istioctlbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-mixcbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-mixsbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-pilot-agentbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-pilot-discoverybefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:1.1::el8servicemesh-proxybefore 0:1.1.17-2.el80:1.1.17-2.el8
Red Hat:service_mesh:1.1::el8servicemesh-sidecar-injectorbefore 0:1.1.17-3.el80:1.1.17-3.el8
Red Hat:service_mesh:2.0::el8servicemeshbefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-istioctlbefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-mixcbefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-mixsbefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-pilot-agentbefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-pilot-discoverybefore 0:2.0.7-3.el80:2.0.7-3.el8
Red Hat:service_mesh:2.0::el8servicemesh-proxybefore 0:2.0.7-3.el80:2.0.7-3.el8

Same product

envoyproxy: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-30255HTTP/2: CPU exhaustion due to CONTINUATION frame flood
    56Plan
  • CVE-2024-27919HTTP/2: memory exhaustion due to CONTINUATION frame flood
    56Plan
  • CVE-2021-29492Bypass of path matching rules using escaped slash characters
    52Plan

Published before and after this one in the same product

  • ← EarlierCVE-2021-32777Aug 24, 2021 · Incorrect concatenation of multiple value request headers in ext-authz extension
    34Monitor
  • ← EarlierCVE-2021-32778Aug 24, 2021 · Excessive CPU utilization when closing HTTP/2 streams
    30Monitor
  • Later →CVE-2021-32780Aug 24, 2021 · Incorrect handling of H/2 GOAWAY followed by SETTINGS frames
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
red hat:servicemesh0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-citadel0:1.1.17-3.el8 · Red Hat:service_mesh:1.1::el8Package registry (OSV)
red hat:servicemesh-galley0:1.1.17-3.el8 · Red Hat:service_mesh:1.1::el8Package registry (OSV)
red hat:servicemesh-istioctl0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-mixc0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-mixs0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-pilot-agent0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-pilot-discovery0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-proxy0:2.0.7-3.el8 · Red Hat:service_mesh:2.0::el8Package registry (OSV)
red hat:servicemesh-sidecar-injector0:1.1.17-3.el8 · Red Hat:service_mesh:1.1::el8Package 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.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, 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).

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
low · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
Low

Weakness class (CWE)

CWE-551 · Incorrect Behavior Order: Authorization Before Parsing and Canonicalization

CVSS vector

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

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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records