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CVE-2021-25762· NVD / CVE Program· CNA mitre

In JetBrains Ktor before 1.4.3, HTTP Request Smuggling was possible.

MediumCVSS 5.3 · v3.1—No exploit No fix recorded
Published
Feb 3, 2021
Updated
Jun 16, 2026
EPSS
0.8% · 55th percentile
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Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

Affected systems

VendorProduct
jetbrainsktor

Affected versions

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

  • jetbrains ktorbefore 1.4.3

Same product

jetbrains: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-12736JetBrains Ktor framework before 1.2.0-rc does not sanitize the username provided by the user for the LDAP protocol, leading to command injec
    40Plan
  • CVE-2023-45612In JetBrains Ktor before 2.3.5 default configuration of ContentNegotiation with XML format was vulnerable to XXE
    39Monitor
  • CVE-2023-45613In JetBrains Ktor before 2.3.5 server certificates were not verified
    36Monitor
  • CVE-2022-48476In JetBrains Ktor before 2.3.0 path traversal in the `resolveResource` method was possible
    30Monitor
  • CVE-2021-43203In JetBrains Ktor before 1.6.4, nonce verification during the OAuth2 authentication process is implemented improperly.
    30Monitor
  • CVE-2020-5207Request smuggling is possible in Ktor when both chunked TE and content length specified
    30Monitor

Remediation

Which version to upgrade to

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

No fix version is recorded for this entry. Check the references for vendor advisories.

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.

EPSS, last 120 days

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.

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
none
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
None
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:N/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.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; 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 help

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

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

All records