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CVE-2021-36154

25
FAUCET Score

CVE-2021-36154 is a denial-of-service vulnerability affecting gRPC Swift versions 1.1.1 and earlier, specifically within the HTTP2ToRawGRPCServerCodec component. An unauthenticated remote attacker can exploit this by sending numerous small messages within a single HTTP/2 frame, triggering uncontrolled recursion and stack exhaustion. Rated with a CVSS score of 7.5 (High), this vulnerability is easily exploitable over the network with low attack complexity, leading to a complete denial of service. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
1.0.0CPE matchmatch criteria
cpe:2.3:a:linuxfoundation:grpc_swift:1.0.0:*:*:*:*:*:*:*
1.1.0CPE matchmatch criteria
cpe:2.3:a:linuxfoundation:grpc_swift:1.1.0:*:*:*:*:*:*:*
1.1.1CPE matchmatch criteria
cpe:2.3:a:linuxfoundation:grpc_swift:1.1.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.08%
Probability of exploitation in next 30 days
EPSS Percentile
79.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0208 is in the 64th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

swiftpatch availablevia ghsa
Product: github.com/grpc/grpc-swiftFixed in: 1.2.0

Vendor Advisories (1)

swiftGHSA-4rhq-vq24-88gwmedium

Uncontrolled Recursion in HTTP2ToRawGRPCServerCodec

May 22, 2023

References

bugs.chromium.org / p/oss-fuzz/issues/detail
Mailing ListThird Party Advisory
github.com / grpc/grpc-swift/releases
Release NotesThird Party Advisory
github.com / grpc/grpc-swift/security/advisories/GHSA-4rhq-vq24-88gw
Third Party Advisory