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CVE-2026-35640

OpenClaw < 2026.3.25 - Denial of Service via Unauthenticated Webhook Request Parsing

6.9 MediumFix available

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.45%Up 0.4 points since Apr 10, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.9

OpenClaw < 2026.3.25 - Denial of Service via Unauthenticated Webhook Request Parsing

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
CVE-2026-35640
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-696
Updated
2026-11-02
EUVDEUVD-2026-21136 6.9

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
EUVD-2026-21136
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-3h52-cx59-c456 6.9

OpenClaw: Feishu webhook reads and parses unauthenticated request bodies before signature validation

Summary

Feishu webhook reads and parses unauthenticated request bodies before signature validation

Affected Packages / Versions

  • Package: openclaw
  • Affected versions: <= 2026.3.24
  • First patched version: 2026.3.25
  • Latest published npm version at verification time: 2026.3.24

Details

Feishu webhook handling previously parsed JSON before signature validation, which let unauthenticated callers force full JSON parsing work before rejection. Commit 5e8cb22176e9235e224be0bc530699261eb60e53 reads the raw request body, validates the signature first, and only then parses JSON.

Verified vulnerable on tag v2026.3.24 and fixed on main by commit 5e8cb22176e9235e224be0bc530699261eb60e53.

Fix Commit(s)

  • 5e8cb22176e9235e224be0bc530699261eb60e53
Record
GHSA-3h52-cx59-c456
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-400
Updated
2026-11-02
GitHub AdvisoriesGHSA-8f9r-gr6r-x63q 6.9

Duplicate Advisory: OpenClaw: Feishu webhook reads and parses unauthenticated request bodies before signature validation

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-3h52-cx59-c456. This link is maintained to preserve external references.

Original Description

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
GHSA-8f9r-gr6r-x63q
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-696
Updated
2026-11-02
NVD 6.9

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
CVE-2026-35640
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-696
Updated
2026-11-02
OSV 6.9

OpenClaw < 2026.3.25 - Denial of Service via Unauthenticated Webhook Request Parsing

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
CVE-2026-35640
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-696
Updated
2026-11-02
OSVGHSA-3h52-cx59-c456 6.9

OpenClaw: Feishu webhook reads and parses unauthenticated request bodies before signature validation

Summary

Feishu webhook reads and parses unauthenticated request bodies before signature validation

Affected Packages / Versions

  • Package: openclaw
  • Affected versions: <= 2026.3.24
  • First patched version: 2026.3.25
  • Latest published npm version at verification time: 2026.3.24

Details

Feishu webhook handling previously parsed JSON before signature validation, which let unauthenticated callers force full JSON parsing work before rejection. Commit 5e8cb22176e9235e224be0bc530699261eb60e53 reads the raw request body, validates the signature first, and only then parses JSON.

Verified vulnerable on tag v2026.3.24 and fixed on main by commit 5e8cb22176e9235e224be0bc530699261eb60e53.

Fix Commit(s)

  • 5e8cb22176e9235e224be0bc530699261eb60e53
Record
GHSA-3h52-cx59-c456
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-400
Updated
2026-11-02
OSVGHSA-8f9r-gr6r-x63q 6.9

Duplicate Advisory: OpenClaw: Feishu webhook reads and parses unauthenticated request bodies before signature validation

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-3h52-cx59-c456. This link is maintained to preserve external references.

Original Description

OpenClaw before 2026.3.25 parses JSON request bodies before validating webhook signatures, allowing unauthenticated attackers to force resource-intensive parsing operations. Remote attackers can send malicious webhook requests to trigger denial of service by exhausting server resources through forced JSON parsing before signature rejection.

Record
GHSA-8f9r-gr6r-x63q
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-696
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
openclaw
npm
 before 2026.3.28
2026.3.28

History

History
RecordedChangedSources
affected
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-35640 is a medium vulnerability (CVSS 6.9) in Openclaw, published March 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.45%, the 39th percentile. Fixed in openclaw 2026.3.28.

References

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