CVE-2021-31920

Q: How do I fix CVE-2021-31920?

Upgrade istio to 1.9.5 or later.

Q: Is CVE-2021-31920 being actively exploited?

Not that we know of. CVE-2021-31920 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 65% of all scored CVEs.

Q: How severe is CVE-2021-31920?

CVE-2021-31920 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2021-31920 affect?

Published advisories record a fix for istio (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

MEDIUM

6.5

CVSS v3

NVD

Description

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

CWE-706

How to fix

Remediation Available

istioNVD

Affected:>= 1.9.0, < 1.9.5Fixed in:1.9.5CVE-2021-31920derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

1.17%probability of exploitation in 30 days

65thpercentile

Moderate risk: more likely to be exploited than 65% of all known CVEs.

References

Exploit1

istio.io

Related Vulnerabilities

Other CWE-706 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-24813	Critical	9.8	100%	KEV	Fix
CVE-2020-15505	Critical	9.8	100%	KEV	Fix
CVE-2021-40539	Critical	9.8	99%	KEV + Ransom	Fix
CVE-2024-27292	High	7.5	69%	-	Fix
CVE-2021-40856	High	7.5	51%	-	-
CVE-2021-24122	Medium	5.9	23%	-	Fix

Common questions

How do I fix CVE-2021-31920?

Upgrade istio to 1.9.5 or later.

Is CVE-2021-31920 being actively exploited?

Not that we know of. CVE-2021-31920 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 65% of all scored CVEs.

How severe is CVE-2021-31920?

CVE-2021-31920 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2021-31920 affect?

Published advisories record a fix for istio (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2021-31920

Markdown

[![CVE-2021-31920](https://tridentstack.com/cve/badge/CVE-2021-31920.svg)](https://tridentstack.com/cve/CVE-2021-31920)

HTML

<a href="https://tridentstack.com/cve/CVE-2021-31920"><img src="https://tridentstack.com/cve/badge/CVE-2021-31920.svg" alt="CVE-2021-31920"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.