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CVE-2025-53940

HIGHCVSS 8.5/10EPSS 2.65%

Last modified

CVE-2025-53940 is a high-severity vulnerability rated 8.5/10 on the CVSS scale. Quiet is an alternative to team chat apps like Slack, Discord, and Element that does not require trusting a central server or running one's own. In versions 6.1.0-alpha.4 and below, Quiet's API for backend/frontend communication was using an insecure, not constant-time comparison function for token verification. EPSS estimates a 2.65% chance of exploitation in the next 30 days.

Description

Quiet is an alternative to team chat apps like Slack, Discord, and Element that does not require trusting a central server or running one's own. In versions 6.1.0-alpha.4 and below, Quiet's API for backend/frontend communication was using an insecure, not constant-time comparison function for token verification. This allowed for a potential timing attack where an attacker would try different token values and observe tiny differences in the response time (wrong characters fail faster) to guess the whole token one character at a time. This is fixed in version 6.0.1.

Metrics

CVSS 4.0
8.5/10

CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/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

EPSS Probability
2.65%

83.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2025-53940?
Quiet is an alternative to team chat apps like Slack, Discord, and Element that does not require trusting a central server or running one's own. In versions 6.1.0-alpha.4 and below, Quiet's API for backend/frontend communication was using an insecure, not constant-time comparison function for token verification. This allowed for a potential timing attack where an attacker would try different token values and observe tiny differences in the response time (wrong characters fail faster) to guess the whole token one character at a time. This is fixed in version 6.0.1.
How severe is CVE-2025-53940?
CVE-2025-53940 has a CVSS score of 8.5/10 (HIGH severity). The EPSS model estimates a 2.65% probability of exploitation in the next 30 days.
How do I fix CVE-2025-53940?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-53940?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST